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NOTES 



ON 



TORPEDOES, OFFENSIVE AND DEFENSIVE. 



MAJOR R, H^STOTHERD, R, E. 




v 



Q 









WASHINGTON: 

•GOVERNMENT PRINTING OFFICE 

1S72. 



P R E F A C E 



The following pages on the subject of submarine mines have been com- 
piled from the various papers which have been drawn up, and experiments 
which have been made during the last three or four years in the course of 
instruction carried on at the School of Military Engineering, Chatham. 
The object in view has been to put the officers and men instructed in pos- 
session of a hand-book, to which they may refer should they, at any future 
time, be called upon to put in practice what they have learned. The course 
of instruction has now been so far perfected, in conformity with certain 
principles deduced from practical trial, that the system taught might at 
any time be adopted for actual service, and as improvements are made, 
they may, from time to time, be introduced. 

A great deal of valuable information has been derived from Captain 
Harding Steward's very interesting " Notes on Submarine Mines," which 
was perhaps the first practical work ever published ou this subject. Lieu- 
tenant S. Anderson, E. E., assistant instructor in telegraphy and sub- 
marine mining, at Chatham, and Lieutenants O. Chadwick, H. Jekyll, 
J. T. Bucknill, K. F. Moore, and R. Y. Armstrong, E. E., who have been 
temporarily attached at various periods to the School of Submarine 
Mining, have been indefatigable in carrying on numerous experiments, 
with a view to perfecting our system, and to them a great deal of credit 
is due. Finally, we have had the benefit of the valuable series of ex- 
periments carried on, and of the information collected, by the floating 
obstruction committee, of which Lieutenant-Colonel Fisher, C. B., E. E., 
and F. Abel, esq., F. E. S., chemist to the war department, were mem- 
bers. These officers have, moreover, contributed personally much valu- 
able information, of which, in carrying on the experiments of the above- 
mentioned committee, they had become possessed. 

Captain \V. Dawson, E. S"., late secretary to the floating obstruction 
committee, has very kindly looked over Chapters XIV and XV, on 
u Clearing Channels of Submarine Mines" and " Locomotive Torpedoes," 
and Commander F. Harvey, E. X., has been good enough to furnish in- 
formation for the description of his sea torpedo. Commander Harvey 
is about to publish a book giving a description of his torpedo, in which 
any farther details concerning it will be found. 



The use of submarine mines as military defensive agents has only 
recently acquired any importance, and progress toward the establish- 
ment of a definite system has led to considerable changes since the first 
of the papers, embodied in this hand-book, was written. It was never 
considered more than an ad-interim publication, and but a small number 
of copies have consequently been printed. It is now proposed to revise 
the whole, bringing it up to date, and to reprint it as soon as possible. 

R. H. S. 

Chatham, 31st March, 1871. 



CONTENTS 



Chap. Page. 

I. Introductory 7 

II. General principles 16 

III. Explosives 28 

IV. Form and construction of case 49 

V. Mooring 62 

VI. Mode of iguitiou 87 

VII. Electric cables 115 

VIII. Water-tight and insulated joints and connections 130 

IX. Submerging mines, &c 151 

X. Electrical igniting agents 163 

XI. Closing electrical circuit 186 

XII. Electrical testing- tables 220 

XIII. Mechanical and electrical tests 238 

XIV, Clearing channels of submarine mines 271 

XV. Locomotive torpedoes 275 

XVI . Approved forms of apparatus 299 

Index 307 



EREATA. 

For "moving," page 9, 14tli line from bottom of page, road " mooring." 
For " outworks of," pane' 12, 2d lino from top of page, read " outworks to." 
For "de ense," page 12, margin, read " defense." 
For "ha," page 13, 17th line from bottom of page, read "has." 
For " ordinary," page IT, 6th line from bottom of page, read "extraordinary." 
For " chanel," page 20, margin, read "channel." 

For " kilograms." page 28, 8th line from bottom of page, read "kilogrammes." 
For '-opinion by," page 32, 20th line from ton of page, read "opinion of.*' 
For "another," page 33, llth line from top of page, read "one another." 
For" was put.'* page 33, 12th line from bottom of page, read " were put." 
For "doubled." page 34, Pith line from bottom of page, read "doubted." 
For '• Van Scheliha," page 44. 16tb line from top of page, read "Von Scheliha." 
For " see page 33," page 47, 5th line from top of page, read " see page 43." 
For •■ Fig. 1, page 15," page 47, 24th line from top of page, read " Fig. 1, page 23." 
For " Figs. 6," page 52, 10th line from top of page, read "Fig. G." 
For " of submarine mints." page 54. 23d line from top of page, read "of the case ul 
submarine min< 
For "V 7 ."' page 55. 19th line from bottom of page, read " : 
Insert at end of 3d Hue, page 50, •• 

For " electric," page 04, 10th Hue from bottom of page, read " electrical." 
For "for recovery," page 09, 13th line from top of page, read " for its recovery." 
For "triangle guys.'' page 71, 10th line from top of page, read " triangle gins." 
For " shore lighter," page 72, 17th line from bottom of page, read " store lighter." 
For "moved," page 73, 10th line from bottom of page, read " moored." 
For " these cables," page 84, 8th line from top of page, read "three cables." 
For "P=0," page 85, 21st line from bottom of page, read "P= 0." 
For "in the metal," page 87, 24th line from bottom of page, read " on the metal." 
For " Rnssans," page 87, 5th line from bottom of page, read " Russians." 
For "miner," page 91, marginal note, read "mines." 
For "miner," page 92, marginal note, read "mines." 
For "Dauiells," page 93, 8th line from bottom of page, read "Daniell's." 
For " moved out." page 94, 20th line from bottom of page, read " veered out." 
For "on mile," page 95, 4th line from top of page, read " one mile." 
For "shoulder (rf)," page 90, 18th line from bottom of page, read "shoulder (ft)." 
After "8 cells," page 97, 8th line from bottom of page, read " (slowly.)" 
For " electric; circuit," page 98, 7th line from top of page, read "electric circuit." 
For " Schino's," page 98, 12th line from top of page, read " Schaw's." 
For "dilute,'* page 99, 1st line from top of page, read " diluted." 
For "(rf' d')" page 103, 1/th line frorn bottom of page, read " (d' d')." 
For "Daniells's,"page 104, 18th, 20th, and 23d lines from top of page, read "Darnell's.' 1 
For " Dauiells," page 105, in heading, read " Daniell's." 
For "Thomson's," page 105, bottom of table, read "Thompson's." 
For "Dauiells," page 100, 12tli line from top of page, read "Daniell's." 
After "not," page 112, 3d line from bottom of page, read "quite." 
For " sewed," page 110, 3d line of description in table, read " served." 
For "sewed," page 110, 14th line-of description in table, read "served." 
For " Siemeus's," page 110, 2d line from bottom of page, read " Siemens'." 
Insert reference letter (b) on center conductor of I^ig. 40, page 121. 
Insert reference letter (a) on main conductor of Fig. 48, page 127. 
For "test," page 129, 14th line from top of page, read "best." 
For "coumpound," page 139, 8th line from top of page, read " compound." 
For "tighly," page 139, 14th line from bottom of page, read " tightly." 
For "Nicolls metallic oint," page 142, margin, read "Xicoll's metallic joint." 
For " insulaled," page 143, 1st line below Fig. 59, read " insulated." 
For "base," page 145, llth line from bottom of page, read " bare." 
For " ext emity," page 151, 9th line from bottom of page, read "extremity." 
For "turued out," page 155, 24th line from top of page, read " towed out.'* 
For "Siemens's," pages 100 and 107, read "Siemens'." 
For "No. 20," page 170, 2d line from bottom of page, read " Xo. 22." 
Strike out "page 100," page 171, 10th line from top of page. 
For "Markus's." page 172, 15th line from top of page, read "Marcus 7 ." 
For "large," page 173, 1st line from top of page, read " larger." 
For " Wallaston's,'' page 177, margin, read " Wollaston's." 
For " is a," page 180, 8th line from top of page, read " in a.'" 
For "Wallaston's," page 185, in table, read "Wollaston's." 



For "changing," page 192, 20th line from bottom of page, read "charging." 
For "point," page 192, 8th line from bottom of page, read "front." 
For " (e)," page 193, 4th line from bottom of page, read " (/)." 
For "change," page 197, 13th line from bottom of page, read "charge." 
For " fuze and," page 203, margin, read " fuze out." 
For "(e)," page 203, 17th line from bottom of page, read "(I)." 
For " page 134," page 206, 17th line from top of page, read " page 147." 
For "page 134," page 206, 11th line from bottom of page, read " page 147." 
For " blow in," page 206, 10th line from bottom of page, read "blow on." 
For " metalic," page 206, 3d line from bottom of page, read " metallic." 
For " moving," page 207," 5th line from bottom of page, read " mooring." 
For "fuze end," page 212, 7th liue from bottom of page, read " far end." 
For " bury it," page 217, 22d line from top of page, read " buoy it." . 
For " supports," page 219, 10th line from bottom of page, read " outposts." 
For " (see page 186)," page 221, 5th line from top of page, read " (see page 199)." 
For "(#,) page 223, 3d line from bottom of page, read " (#i)" 
For " (#)," page 224, 13th line from top of page, read " (#i)." 

For "passing the coils," page 228, 22d line from top of page, read " passing through 
the coils." 

For "deferential," page 242, 5th line from top of page, read "differential." 

For " batten," page 242, 9th line from bottom of page, read " battery." 

For " pages 94 to 96," page 243, 15th line from top of page, read " pages 104 to 106." 

For " reconnected," page 244, 11th line from top of page, read " connected." 

Page 244, at beginning of 8th line from top of page, insert " to." 

For " Siemens's," page 250, 20th line from bottom of page, read " Siemens'." 

For " page 215," page 258, 17th line from bottom of page, read " page "216." 

Insert reference " (0)," page 259, on Fig. 107, to right of " c." 

For "Z," in equation (12), page 261, read "z." 

For "page 215," page 265, 21st line from bottom of page, read "page 216." 

For " page 88," page 267, 4th line from top of page, read " page 98." • 

For " to all where/' page 269, 4th line from top of page, read " to all stations w here." 

For "as far," page 272, 18th line from bottom of page, read " so far." 

For "train mortars," page 273, in marginal note, read "twin mortars." 

For " sluices," page 291, 20th line from bottom of page, read " sluice." 

For " mushroom anchor," page 303, margin, read " mushroom sinker." 

For "canvass," page 289, 7th line from bottom of page, read " canvas." 

For Fig. 93, page 224, substitute cut : 





CHAPTER I. 

INTRODUCTORY. 

The term torpedo has been hitherto applied, in a vague 
kiud of way, to all the numerous contrivances which have, 
from time to time, been devised for producing submarine 
explosions calculated to act destructively against ships in 
their immediate vicinity. This term has been used whether 
these engines have been arranged defensively, the charge 
being ignited when a vessel is within range of their sphere 
of explosion, or whether offensively, that is, in a movable 
form for the attack of a vessel at anchor, or as a means of 
offense against a vessel in chase of a ship possessing the 
necessary apparatus, or under whatever circumstances they 
have been employed. 

This term, "torpedo," does not seem applicable to defen- Definition of a 
sive mines, or those which would be used to block up the submarine miue - 
channel of a river, or the approaches to a fortified sea-port, 
or in any other similar position,- in fact, occupying a site 
analogous to that of a system of countermines in connection 
with a land fortress. In the following pages, therefore, I 
propose to call all contrivances of the above nature, used 
for defensive purposes, "submarine mines," leaving the Definition of a 
term "torpedo" for all offensive combinations, to which it ° rpe 
seems to be much more applicable. 

Under the comprehensive head of submarine mines is 
included a vast field for research, in which there is ample 
space for the development of inventive genius, in connection 
with the defense of fortified harbors, estuaries of rivers, and 
the coast generally, a most important subject in a military 
point of view, and which, affecting as it does the attack of 
such places from the sea, renders it a consideration of the 
utmost gravity. The introduction of machines of this nature 
in war cannot be overlooked with impunity by a great 
maritime power like Great Britain, possessing, as she does, 
numerous colonies and an immense commercial navy which, 
in addition to her own coasts, must be defended in the 
event of war; and as the employment of submarine mines 
seems to present such a considerable increase in defensive 
power, there is every reason to suppose that a judicious use 
of them would, on an emergency, prove of infinitely greater 
value to us than to a nation possessing less of the maritime 
element in its composition. 



8 

Chinese subma- Submarine mines have, from time to time, been used in 
warfare. A very curious Chinese illustrated description 
of a system of this nature was brought home very recently 
from that country. The method of ignition of the charges 
in this Chinese system appears to have been exclusively 

Russian sutma- arranged for mechanical action. Similar contrivances were 

ins mines. 

also used by the Eussians in the defense of the Baltic dur- 
ing the Crimean war, without, however, any great amount 
of success. These seem also to have been designed for me- 
chanical action, as regards the ignition of the charge; but 
though several of them were fired by contact with the ves- 
sels of the blockading fleets, the damage done was insignifi- 
cant, the charges of powder used being comparatively small 
submarinein amount. Again, in the recent civil war in the United 

mines, used in n .. . . . • 

civil TvarinAmer-btates of America, submarine mines were extensively used 
both by the Federals and confederates, especially by the 
latter, with very much more decisive results. Several of 
the Federal vessels were sunk, and many were so seriously 
damaged as, for the time, to be placed hors de combat. An 
excellent description of the means employed during this 
war has been given by Captain Harding Steward, Royal 
Engineers, in his valuable jmmphlet on submarine mines, 
which contains much information on the practical working 
of these machines and of the difficulties necessarily to be 
encountered therein. A very decided advance in submarine 
mining is evinced in the arrangements made during this 
war; the machines used by the Eussians in the Baltic were 
simply allowed to driit, and were fired by mechanical means, 
thus rendering them equally dangerous to friend and foe, 
whereas here, we find the confederates mooring their charges 
in certain positions and firing them, not only by mechanical 
but, toward the end of the war, by electrical agency — a 
very decided step in advance, as, in this way, they could at 
will be rendered perfectly harmless to a friendly vessel, 
while their chance of acting destructively against an enemy 
was vastlv increased. Another improvement noticeable is 
the increase in the amount of powder employe I in each 
charge, regulated according to certain rules derived from 
experiment; the charges were, however, still insufficient. 
Austrian s u l) ., Theresults arrived at during this war were so decided, 
that the investigation of the subject of submarine mines has 
since become almost general among civilized nations; and 
we find them again used by the Austrians, for the defense 
of Venice, Pola, and the coasts of the Adriatic during their 
war against Prussia and Italy in 1806. I am not aware that 
any opportunity occurred of testing the efficiency of the 



Hiariuf. mines-'. 



system employed during this war, against an enemy's ship, 
but the whole was exhibited at Paris in 1807. An exami- 
nation of this apparatus again shows an advance in the 
science of submarine mining, for, whereas in the confederate 
system, everything was to a certain extent tentative and 
hurriedly arranged, here we have working patterns of all 
the materials and apparatus on a certain system, and capa- 
ble of being rendered available for any service required, by 
a simple reproduction of the number of articles necessary 
according to patterns which, after numerous experiments, 
had been decided on. The arrangement and construction 
of the equipment exhibited shows a considerable amount of 
ingenuity, and reflects much credit on the designer, Baron 
Von Elmer, of the Austrian Corps of Imperial Engineers. 

In this country a committee was appointed, in 1863, to Floating oo- 

, . ' n . . . , . . . . . , . .. e . struction commit- 

investigate this subject, in combination with that ot passive tee appointed. 
obstructions, and their labors are now concluded. An im- 
mense number of experiments have been made under their 
supervision, with a view to the determination of the details 
of the apparatus, &c, best suited for the purpose; and many 
of these experiments have been carried on by the officers 
and men of the Royal Engineers, at Chatham. 

Instruction in the theory and practice of electricity and course of in- 
its application to the ignition of gunpowder and other ex- cha7ha C m. loa 
plosive agents, for mining purposes, both on shore, under 
water, and also as required in connection with a system of 
submarine mine, has for some time been given in the School 
of Telegraphy, at Chatham. The subject is, however, of 
such vital importance that it has become necessary to ex- 
tend the scale of instruction, from the small and make-shift 
way in which it has been taught, to such a system as would 
be required on actual service ; and for this purpose a moving 
lighter and a certain number of boats, anchors of various 
kinds, cases to represent submarine mines, chains, cables, 
&c, together with batteries, circuit-closers, and other elec- 
trical gear have been provided, and with these theinstructiou 
is now carried on. 

Submarine mines may be divided into two great classes, offensive mines 
offensive and defensive. The first, the offensive class, which ° r 
it is proposed to designate by the term " torpedo," hitherto 
popularly applied to all, falls more particularly to theprovince 
of the navy, though its use must not, on that account, be 
neglected by the military branch of the service. It includes 
every class of device designed for the active attack of ves- 
sels, whether arranged at the end of a spar or boom, in 
connection with a properly -tit ted torpedo-boat, to be used 



10 

in ramming an enemy's ship or to be carried on board snip 
and thrown out with a view of acting against a vessel in 
chase, and exploded by electricity or mechanically, when in 
actual contact with her, or to be used for the attack of a 
vessel at auchor. To this class also belong drifting torpe- 
does, or those propelled by any mechanical arrangement 
through the water, and of such a form as would be applica- 
ble for the attack of floating or other obstructions, or of 
ponton-bridges, &c. Instruction in such appliances is now 
regularly conducted on board Her Majesty's gunnery ships 
Excellent and Cambridge, and a very good practical book, 
in connection with this course, has been drawn up by Lieu- 
tenant Fisher, E. N., who has charge of this duty on board 
the former vessel. The men ot the Royal Engineers should 
be thoroughly practiced in the use and handling of such 
contrivances, especially with reference to the attack of pon- 
ton-bridges; and it is necessary that they should be well 
practiced in the demolition, by torpedoes, as well as in the 
construction of booms and other passive obstructions. As 
yet, however, but little has been done in this respect, our 
attention and time having been chiefly devoted to the de- 
velopment of a system of defensive mines. A torpedo-boat 
has, however, been designed and is constantly used during 
the course of instruction given on board Her Majesty's ship 
Excellent. 

To the naval branch of the service would seem chiefly 
to appertain the designing and practical use of the apparatus 
adapted for searching for and carrying off an enemy's mines, 
and the defense of vessels against mines of every class, 
whether stationary or drifting. 

We now come to the second great class of these contri- 
vances, viz, the defensive or the submarine mine proper, 
which I propose so to designate, in contradistinction to 
the torpedo or attacking implement, and especially the mil- 
itary engine. 
Defensive These seem applicable to almost any circumstances, and 
due e miues proper, may be used witli a very great advantage to the defense, in 
innumerable instances, from that of a first-class sea-coast 
fortress against a first-class fleet of iron-clads, to that of a 
fishing village against a small privateer. This assertion 
seems to be strongly borne out by the experience we have 
gained, from the perusal of the accounts of the naval opera- 
tions, during the late civil war in the United States of 
America. During that war the iron-clad, and even wooden 
vessels of the Federal fleet, frequently silenced and ran past 
confederate shore batteries, the latter armed with numerous 



11 

and well-served pieces of heavy caliber, rifled as well as 
smooth-bore. For example, Forts Jackson and St. Philip, 
defending the entrance to New Orleans, and mounting about 
100 heavy guns, with the advantages of numerous shoals 
and a swift current, failed to stop a squadron of wooden 
ships, which ran past them after a few days' bombardment 
from their mortar-vessels. Again at Vicksburgh, after a 
short bombardment, the Federal fleet ran past the batteries 
commanding the river, with the loss of only a few men, sub- 
sequently passing down again with a similar result. On 
this occasion there were about 30 guns in the shore batteries 
against 40 on board the ships ; some of the vessels were, 
however, ironclads. 

Again, at Fort Fisher, at the mouth of Cape Fear Eiver, 
leading to Wilmington, the confederate guns were on two 
occasions silenced by those of the Federal iron-clad fleet. 
These are only a few of the numerous instances in which 
similar results were obtained — in fact the obstructions and 
submarine mines of the confederates gave much more trouble, 
and caused much more delay and damage to the Federal 
fleets, than the batteries. Witness the notable example of 
Charleston, where, though the guns of Fort Sumter were 
silenced over and over again, the vessels were kept out for 
months by the obstructions and submarine mines. Admiral opinion of Ad- 
David D. Porter, of the United States Navy, in his very united s°tatVs 
able report on the defensive powers of coast-batteries, states: Navy * 
"The running past a battery is a very easy thing when 
there is a straight channel and sufficient depth of water ; 
and there is no fort in any of the waters of the North that 
cannot be safely passed, and (in military phrase) the posi- 
tion turned; and no forts now built can keep out a large 
fleet, unless the channel is obstructed." And again, " Ob- 
structions and torpedoes are a better defense than our 
present forts." Such is the deliberate opinion of a very able 
naval officer, given alter an experience of three or four years 
in the attack of water batteries of every variety; and what 
has been done once may, no doubt, be done again. Though 
it cannot be said that shore-batteries may not be very much 
improved, and their defensive powers against shipping 
greatly increased, taking them gun for gun as against an 
attacking fleet, there seems to be sufficient data to show 
that the defensive power of the very best fort that can be 
built will be much increased by a judicious arrangement of 
obstructions or submarine mines, or a combination of both. 
If used in the defense of a first class fortress, such as Ports- Defense of n 
mouth, for example, they should be so arranged as to be asVorSnouti!^ 



12 

covered by the guns of the forts and floating batteries, so 

that while acting as outworks of these latter, they would be 

protected by them from disturbance by the boats of a hostile 

fleet. 

De ense of a Another case, in. which submarine mines could be effect- 
mercantile harbor, 
as Liverpool. rvely used, is that of a great mercantile harbor defended by 

forts carrying a few heavy guns, as Liverpool, for example- 
Here we have a few guns in position, which might be 
silenced by a sufficiently powerful hostile fleet; but if a 
judicious arrangement of submarine mines were added to 
these, placed in such a position as to be covered by the 
guns, and by those of such vessels of war as might be at 
hand, and, at the same time, advanced sufficiently far to 
prevent the guns of an enemy's vessels from reaching the 
shipping in the port, the position as regards the defense 
would be immensely improved. 

In all cases, by a very simple arrangement, to be hereafter 
described, the channel could be made perfectly sate to 
friendly vessels, which could run in and out at pleasure, 
while it could at any moment be made instantly dangerous 
should an enemy attempt to follow. 
useful in an rm- A third case, in which submarine mines could be used 
It Belfast. harbor ' with advantage, is that of the estuary of a river leading to 
a mercantile harbor and not necessarily defended by forts 
of any sort, as for example Belfast. This important port is sit- 
uated a considerable distance up an arm of the sea, on a 
river, and is, or used to be, so nearly undefended by guns 
that, for the sake of example, they need not be considered 
as an item in its defense. Under present circumstances 
Belfast would be open to the attack of a comparatively small 
fleet of hostile vessels, and its destruction would be a very 
serious blow in a commercial point of view. If a well-ar- 
ranged system of submarine mines, however, were placed 
in the estuary of the river, with one or two gun-boats or a 
floating-battery, to prevent boats from searching for them, 
the place would be quite sale from any sudden attack, and 
would be capable of holding out against an enemy's squad- 
ron, with a fair prospect of success, .till relieved. Mere again 
the mines must be placed at such a distance as to keep hos- 
tile vessels where their fire would be ineffective against the 
shipping and town. Should no gun-boats or floating-bat- 
teries be at hand, a few guns in an earthwork, to cover the 
mines, would be advisable, hut even without them a defense 
on this system might still be carried on, and it would only 
be necessary to put down a greater number ot mines, so 
that one might occasionally be hied at a boat engaged in 



*3 

grappling for them, as a deterrent. As a rule they should 
not, however, be thrown away at small boats, but reserved 
for more worthy objects. 

Another instance in which submarine mines might be ha ? b e f r b n8 a 8 of ^" 
advantageously employed, without any combination of pro- b y- 
tec ting guns, is that of a harbor close upon the sea, which 
could be easily reached by an enemy's guns ; such a place 
as Whitby, for example, which affords a port of considerable 
importance to the coasting and fishing trade. A few sub- 
marine mines laid 4,000 or 5,000 yards to seaward from this 
place would, by the fact of their existence, deter an enemy's 
vessels from approaching, as the advantage to be gained 
would not be worth the danger incurred, while a harbor of 
refuge would be secured to friendly ships. In such a posi- 
tion as this, it might not be practicable to use them at night 
or in a fog, unless some means were adopted for signaling 
the approach of an enemy. 

Again, they might be used for the protection of such a Defense of town 
place as Brighton, where no harbor exists, but which is quite Brighton. b 
open and assailable from the sea, and any attempt to defend 
which with guns could only end in its destruction by bom- 
bardment. In such a case a few submarine mines, placed 
at a distance of a few thousand yards to seaward, would 
exercise a salutary deterrent effect. These mines should 
also be rendered inactive at night or in a fog, to prevent 
accidents, unless some means of signaling were adopted. 

Another case in which they might be usefullv employed, Defense of a 

1/0 « . j. «/ 7 open beach. 

is that of a flat open beach, on which an invading force 
might be landed with facility, as, for example, Sandown 
Bay, in the Isle of Wight. At this point a strong fort ha 
been built in connection with the defenses of Portsmouth? 
to prevent such a contingency. A few submarine mines 
judiciously placed in such a position, and covered by the 
guns of the fort, would, I imagine, vastly increase the chance 
of a successful defense, and act as a deterrent against any 
attempt to kind; and probably in many similar positions a 
smaller fort, only carrying a sufficient number of guns to 
protect the submarine mines, would answer the purpose. 

One use to which submarine mines may be applied must Protection of a a 
not be forgotten; it is that by their means an inferior fleet m el 
has the power of placing an impassable barrier between 
itself and an enemy, reserving, however, the power of pass- 
ing out when required, and of retreating to a strong position 
at any moment, should it be unable to cope with its adver- 
saries. A fleet of merchant-vessels might also, so to speak, 
be similaiiv intrenched. 



.14 

Defe^e by sub- The above are a few of the cases in which it seems that sub- 
marine mines spe- 
cially applicable marine mines could be used with effect, and there are, no 

to Great Britain , , ,.,.,,, 

and Ireland and doubt, many others which might be enumerated, and even a 

our colonies. ., . „ , , . . 

cursory consideration of the advantages to be derived gives 
an impression of their importance, to a country with such 
a great length of coast as that of Great Britain, Ireland, 
and our colonies to be defended. They seem especially 
adapted for the defense of colonial ports, many of which, 
under present circumstances, would be at the mercy of a 
comparatively small squadron of an enemy's vessels, or 
even a single ii on-clad, which could probably run past or 
silence the few guns defending them, and bombard or lay 
the port under contribution. The presence of a few well- 
placed submarine mines would, however, completely alter 
the state of affairs and render a different mode of attack 
necessary. There would then be no alternative but to begin 
the tedious and dangerous operation of clearing the chan- 
nel, or to land and attempt to capture the place without the 
aid of the ships, in which latter case the defenders would 
stand a fair chance of success in dealing with the attacking 
force, which would then probably be acting at a disadvan- 
tage, or, at best, on equal terms only. Another point 
gained would be, that each port so defended would become 
a harbor of refuge into which a friendly vessel could pass 
freely, but which would be effectually barred against an 
enemy in pursuit. In case of war it would be no uncommon 
thing for a friendly vessel to be chased into one of our har- 
bors, as, for example, Melbourne. In such a case a system 
of submarine mines would be invaluable. Finally, sub- 
marine mines may be used in combination with, or without, 
passive obstructions of every variety. 
Moral effect The experience of the late civil war in the United States 
teaches us that the moral effect of a system of defense by 
submarine mines would be very great. Men will face a 
known danger readily, but it is not so with a hidden one. 
The result, therefore, would be a, considerable Increase of 
caution in the mode of approach over places where subma- 
rine mines were supposed to be lodged, with a corresponding 
delay and loss of time in the attack, which, in many cases, 
would enable the defenders to hold out till relieved. Sup. 
pose, for example, such a place as Liverpool were attacked 
by an enemy's squadron, in its present state, protected as 
it is by a few moderately strong forts, past which iron-clad 
vessels might run without serious loss; it would be at the 
mercy of an enemy. If a judicious arrangement of subma- 
rine mines were, however, added to the present guns, the 



15 

same squadron could not get in in tins off-hand way, and 
would probably uot think it worth while to incur any delay 
in attempting to force a passage, as, by the aid of the elec- 
tiic telegraph, it is more than probable that a strong re- 
lieving squadron would be off the port before many days 
had passed. 

There is one very important consideration with reference Co*t ebmpara 
to this question, viz, that the cost of a system of defense, 
by submarine miues, is comparatively trifling. A channel 
1,000 yards wide might, in this way, be defended at an out- 
lay not exceeding that incurred in the purchase of half a 
dozen heavy rifled guns, to say nothing of the ammunition 
required for a modern artillery armament, the cost of which 
is considerable, or of the works in which the guns are placed. 

Again, the materials required in the construction of the Material 

„ „ .-, , , obtainable. 

apparatus are ah articles of commerce, easily procurable; 
the submarine cables, which would perhaps be the most 
difficult part of the equipment to obtain in out of the way 
places, may always be kept in store and laid down when 
required. And finally a system of defense, by submarine 
mines, can be worked by a comparatively small number of 
men. All these are important points in connection with 
a subject which seems capable of such universal application, 
especially when viewed with reference to the defense of our 
numerous and distant colonial possessions. 

The advantage to be derived from the use of submarine Advantage; 

great increase in 

mines is a very considerable increase in defensive power, defensive power. 
One important point is that of setting free our fleet to act 
at sea against that of an enemy ; as a very much smaller 
naval force would be required for harbor defense, and it 
might consequently be concentrated and used to greater 
advantage in active operations. Another is the addition, 
to a very considerable extent, of the defensive powers of 
our coast batteries and fortresses; that addition being ob- 
tainable at a comparatively small cost and with a compara- 
tively small number of specially trained men. A third is 
the acquisition of a power to defend places which have 
hitherto been deemed indefensible. A fourth is the power 
of converting every British harbor into a port of refuge, 
accessible at any moment to friendly vessels, but absolutely 
impassable to an enemy. 



CHAPTER 11. 

GENERAL PRINCIPLES. 

Nature of sui- We will now proceed to consider, in general terms, the 
nature of submarine mines. They may be briefly described 
as charges of gunpowder, gun-cotton, or other explosive 
agent, of various sizes up to 2,000 pounds of gunpowder, or 
its equivalent, inclosed in water-tight cases of iron or other 
material, and placed under water at such depths that, by 
their explosion, they may sink or seriously damage a vessel 
passing in their vicinity. They may be classed under two 
heads, viz : Mechanical, those which depend for the explo- 
sion of the charge on mechanical means, such as the simple 
percussion of a vessel coining in contact with them; and 
electrical, those which are fired by electrical agency, either 
by the vessel herself closing the circuit, or at will from the 
shore. The details of the arrangements in both these sys- 
tems shall be considered hereafter. 
Mechanical The former class, or mechanical mines, are capable only 
Eubir.au ,e mims. of yery limited use# Wheil once p i aced iu a channel it 

becomes equally impassable to friend and foe; they are 
therefore only applicable to certain cases, as, for example, 
where it becomes necessary to block up a channel completely, 
that is to say, to render it altogether impassable till the 
mines have been again removed ; for instance, to inclose 
an enemy's fleet and thus limit its sphere of action, or under 
any similar circumstances. They might be employed on a 
flat beach, dry at low water, to cover the flanks of electrical 
mines defending the navigable channel ; in such a case they 
could be placed in position or removed at low water in com- 
parative security, and the number of electrical cables, &c, 
required might, by such an arrangement, be reduced. They 
Disadvantages, would not be applicable to the formation of harbors of ref- 
uge, as previously alluded to, where merchant-ships could 
run in to avoid an enemy. 

It would be absolutely necessary to make some arrange- 
ment so that they might be exploded at will, as the most 
effectual way of getting rid of them when it became neces- 
sary to clear the channel, as the process of removal in the 
ordinary way, by boats, would be far too dangerous an 
operation to undertake ; in lixct, it would be difficult, nay, 
almost impossible, to get men to do it. 



17 



They possess the advantages of being capable of being Advantages. 
kept in store and made ready for use at short notice ; they 
require no knowledge of electricity in their preparation and 
management ; and they might be used in certain cases with 
advantage, where electrical submarine mines are not ob- 
tainable. 

The second class of submarine mines are those to be tired Electrical sub- 
by electrical agency. These admit of a very much larger mc 
field for their employment. They may be fired either at 
will, (the position of a vessel with regard to them being de- 
termined by the judgment of an observer, who himself com- 
pletes the circuit, so that the charge may be exploded at 
the right moment,) or the vessel herself may be made to com- 
plete the circuit, causing a current to pass and fire the 
charge. 

The disadvantages of electrical submarine mines, as com- Disadvantages. 
pared with those fired by mechanical means, are the multi- 
plicity of wires required, and the necessity of having a cer- 
tain number of specially trained men ; but as the number 
of such men would be comparatively small, this is not of so 
much importance. 

The advantages of electrical submarine mines are, that Advantages. 
they are always absolutely under the control of the observer 
in charge of them. By simply detaching the voltaic battery 
used to fire them, which may be done by the removal of a 
connecting-plug, they become perfectly harmless, and 
friendly vessels may pass over them with safety, which is 
not the case with those arranged for mechanical ignition. 
Again, they can be rendered active at a moment's notice, 
by simply inserting the plug connecting the voltaic battery. 

One great advantage arising from the use of submarine 
mipes is, that no vessel can pass through a channel, pro- 
tected in this way, at night, or in a fog, without affording 
a means of indicating her presence, and thus they are a 
great safeguard against an attack by surprise. In this 
respect the electrical system has a very great advautage ; 
mechanical mines would no doubt act and be fired when 
struck, but the electrical need not necessarily be fired, and 
are capable of being arranged, in a very simple manner, so 
that without being ignited, they may indicate that a vessel 
has passed over the charge. Except in ordinary cases, it would 
not be advisable to throw away a mine in damaging or sinking 
a small boat, as a gap would thus be made in the line, giv- 
ing a safe passage to more formidable vessels ; taking this 
into consideration, therefore, there is again an advantage 
in favor of the electrical system, for the mechanical sub- 



A safeguard 
against a surprise. 



18 

marine mine must act, whatever be the size of the vessel 
striking it, whereas the electrical one may be reserved at 
pleasure for an object worthy of the expenditure of the 
charge. 

Fresii mines can Another advantage of *the electrical system is, that when 
a charge has been fired, or become ineffective from any 
cause, another can be laid down in its place, and the gap 
thus formed in the line made good, unless an enemy is in 
such a position as to be able to prevent it. To perform 
such an operation with safety, it would only be necessary 
to render the neighboring mines for the time being inactive 
so that a boat might pass over them in safety to the point 
required. Should a break occur in the mechanical system, 
by the ignition or destruction of a charge, there it must 
remain ; for it would be impossible to get men to risk the 
chances of being blown up in replacing it by another, and 
even if volunteers for such a dangerous service could be 
procured, the chance of creating a greater opening by the 
accidental explosion of other charges would be so consider- 
able that it would not be prudent to attempt it. 

can be tested Perhaps the most important advantage of the electrical 

electrically. t tr ■ . o 

system is the power of testing electrically, without going 
near it, the condition of each separate charge, at any moment 
after submersion, and of ascertaining, with almost absolute 
certainty, whether it can be fired or not. If in the electrical 
system the charges were grappled by an enemy and carried 
away, the disconnection of any particular charge or charges 
would be indicated, and the removal of such charge or 
charges would be at once made known to the defenders by 
the electrical tests employed. No such power exists in con- 
nection with the mechanical system. 
dm be raised Again, in the electrical system a charge may be taken up 

tor examination. . „ . . . - ,.■--, • 

at any time for examination with perfect safety, whereas it 
would be very dangerous to attempt such an operation in 
the mechanical system. 

captain stew- In making these remarks, with reference to the disad- 
mems'iumediani- vantages of mechanical submarine mines, it must not be 
forgotten that some very important improvements in their 
construction have recently been suggested by Captain 
Harding Steward, Royal Engineers, which would make 
them very much safer to handle and even to raise after sub- 
mersion, but even with the additions proposed by him, they 
would not be capable of being as easily and safely manipu- 
lated as mines on the electrical system. Captain Harding 
Steward's system shall be explained in detail hereafter. 

Danger in sub- Daring the recent war with Russia many of their infernal 

merging mechani- , . .. ., n '« ., , , , , , 

cai mines. machines, as they were called, failed to explode on contact 



19 

with the vessels of the blockading squadron ; this is ac- 
counted for by the fact that the men employed to place 
them in the water were afraid to remove the guards and 
contrivances arranged to make them safe to handle. This 
was found to be the case in some of the torpedoes picked 
up by the boats of the blockading squadron, and with such 
very dangerous machines it would no doubt occasionally 
occur. Captain Harding Steward's suggestions would in a 
great measure obviate the chance of such an occurrence, by 
reducing the danger to be incurred during the process of 
submersion very materially. 

We will now proceed to consider the positions and ar- 
rangements by which submarine mines may most advan- 
tageously be made to offer the greatest possible obstacle to 
the advance of an enemy's vessels. 

In an Austrian work, somewhat corresponding to the Corps Project for the 
Papers of the Royal Engineers, .entitled " Mittheilungen ^uVmJrTne 
iiber Gegenstiinde der Ingenieur- und Kriegs-Wissenschaft- o"bSructions USsivt 
en, herausgegeben vom kaiserlich-kouiglichen Genie-Comite, 
Jahrgang, 1867," the following description is given of the 
method proposed for fortifying the entrance to the port of 
Venice during the war in 1866, (which arrangement was 
not, however, carried out.) Three booms, or passive ob- 
structions, were proposed; the outer one, that next to the 
enemy, to be of light construction, the inner two to be as 
strong as they could possibly be made ; between the two 
heavy booms a double row, in echelon, of submarine mines, 
to be fired by the contact of a vessel, were to have been 
placed, and inside the inner heavy boom what are termed 
" mines of observation " were to have been arranged ; these 
latter were designed to have been fired at will, and were 
intended to come into play had any vessel of the enemy's 
fleet succeeded in passing through the obstructions above 
described. The light outside boom was probably intended 
as a protection against drifting torpedoes or ship's boats, 
Avhich might be sent to attempt to damage the heavier 
booms and render them less resistant to the passage of large 
vessels. The whole was covered by the fire of the guns of 
the place. 

Count Von Scheliha, of the engineers of the late Confed- von schemm> 
erate States, gives in his Treatise on Coast Defense, pub- obstmc^/ous ™!j 
lished in 1868, an account of several forms of submarine submariae raine * 
mines and torpedoes used during the late war, and of their 
effect in certain cases. He is of opinion that submarine 
mines alone are not a sufficient obstruction against an 
attacking fleet; that they should always be combined with 



20 



To close a chan 
el completely. 



passive obstructions of the heaviest character possible, and 
be well covered by guns, to prevent a search being made 
for them by an enemy. 

In shallow waters he proposes to use passive obstructions 
of the heaviest nature, resting on the ground. When the 
water is of such a depth as to preclude the use of passive 
obstructions resting on the bottom, except at an enormous 
outlay of time, money, materials, and labor, he proposes 
to use very heavy floating obstructions securely moored ,* 
and he would use his submarine mines for places where, in 
consequence of the depth of water or the strength of 
the current, ground or floating obstructions would be either 



very difficult to make and 
altogether impracticable. 
Where a free channel is 



keep in position, or would be 



To preserve ^ „uviv« ±*.w v^cu^^x *« x^m^^^vi, ,. ul vu m« r , uv„v/.vi, 
free and yet de- . • , . i 

■ftmsibie passage, be closed at will against an enemy, he proposes to use elec- 



Von Scheliha 
expe 
gai: 
cbanical mines. 



required, which may, however, 
n< 
tricity as the exploding agent. 

His experience has been gained chiefly with self-acting 
Sd^with me y mechanical torpedoes, and he gives much interesting infor- 
mation on their construction, and advantages, and defects, 
under various circumstances. Electrical exploding arrange- 
ments were not much used by the confederates during the 
war, but they used mechanical self-acting mines very exten- 
sively, both on shore in covering defensive works, and under 
water for attacking as well as defensive purposes. Since 
his book was written electrical and other improvements have 
been made in the construction and arrangement of submarine 
mines, and in their present form there is no doubt they may 
be used with advantage in many places, without any 
combination of passive obstructions. These latter would 
no doubt prove most useful in rivers and narrow chan- 
nels, where the force of the current and other conditions 
may be favorable to their employment, but there are 
many places, an open roadstead such as Spithead, for ex- 
ample, where it would be extremely difficult, if not impossi- 
ble, to employ passive obstructions, but where there is every 
probability that submarine mines could be effectively used. 
General rules. The following general rules must be borne in mind with 
reference to any system of submarine mines. 

1st. They may be used in combination with floating and 
grounded obstructions, or without them. 

2d. They should be placed in such positions that their 
explosions shall not injure any passive obstructions com- 
bined with them, or destroy the electric cables of adjoining 
mines. 

3d. At least two, and, where practicable, more rows of 



21 

mines should be arranged in echelon across a channel to be 
defended. 

In deep water it is more necessary to employ several 
lines of mines than in shallow, because in the latter case a 
vessel sunk by a mine would herself offer an impediment to 
others following, but in deep water the explosion of a mine 
leaves a gap, through which there is a safe passage, as far 
as the line of mines in which it occurs is concerned. 

4th. As a general rule submarine mines should be placed 
in the channels through which large vessels only can pass ; 
the shallower portions being, in all cases where such a 
course is practicable, rendered impassable by passive ob- 
structions resting on the bottom. 

5th. Submarine mines should be placed in the narrowest 
parts of a channel. The advantages of such positions are 
evident, as a smaller number would answer the purpose. 

Oth. Where the depth of water and other circumstances 
admit of it, a submarine mine should always rest on the 
bottom : under such circumstances all complications origi- 
nating in mooring arrangements are avoided ; its posi- 
tion is more easily defined, and it is not so easily dis- 
placed by accident, or discovered and destroyed by an 
enemy. 

7th. No indication of their position should be allowed to 
appear on the surface of the water. Under certain condi- 
tions it may be impracticable to conceal them altogether, 
as, for example, where there is a large fall of the tide; under 
such circumstances the smallest x)ossible indication of their 
position must be allowed. 

8th. Where, from the depth of the water, the charges can- 
not be placed on the bottom, they should be so moored as 
to float from 15 to 40 feet below the surface. In places 
where there is a considerable rise and fall of the tide, 
special arrangements would be necessary. 

Oth. The place in which the voltaic batteries and instru- 
ments, connected with the ignition of electrical submarine 
mines, are arranged, should be in those portions of the de- 
fensive works which are likely to be held longest, so that a 
command may be kept over the mines to the latest possible 
moment in the defense. 

10th. Great care should be taken to lay the electric cables 
in such positions as to render their discovery by an enemy 
as difficult as possible. The confederates used many 
devices to conceal the conducting wires of their mines, and 
among others, that of carrying them in by circuitous routes 
and burying them under ground, to discover which, the 



22 

Federals dug trenches across the courses which they would 
be most likely to take. 

11th. The position of the mines should be well covered 
by the fire of the guns of the forts or floating batteries of 
the place to be defended, to prevent their disturbance by 
boats. 

12th. Submarine mines should not be thrown away by 
firing at small boats, except under very exceptional circum- 
stances, but should be reserved for larger vessels. 
General princi- The object to be attained, in arranging any system of 
a channel. mines for the defense of a channel, is to place them in such 

a position that a vessel in passing along that channel must, 
at some one moment, whatever course she may take, be in 
such a position as to come within the radius of destructive 
effect of one of the mines during her progress. In order to 
attain this end it would only seem necessary to place the 
mines so that the circles described by their radii of destruc- 
tive effect may at least touch each other. Theoretically this 
is no doubt the case, but practically such a system presents 
difficulties which would prevent its being worked out, and 
moreover has certain disadvantages inseparably connected 
with it. Among the practical difficulties is the danger of 
entanglement between the mooring cables of adjacent mines 
or their circuit-closers, especially when there is any rise or 
fall of the tide ; when mines are very close to each other it 
is practically impossible to prevent entanglements of this 
nature, even with the most perfect mooring arrangements- 
Again, when mines are very close to each other, the explo- 
sion of one is very likely to injure its neighbors, or, where 
an electrical system of explosion is adopted, to disturb the 
circuit- closers, electrical cables, &c, connected with them. 
And the difficulty of paying out the electrical cables and 
arranging the gear in connection therewith, as well as the 
grappling for and raising a mine for examination, is much 
increased by this very close and precise formation. In fact, 
a certain amount of latitude, so to speak, is absolutely 
necessary in order to simplify the operation of mooring. 
d i a advantages Ainong the positive disadvantages of such an arrangement 
is the fact that if a breach were once made in such a line, 
that breach would, till repaired, afford a safe passage to 
an enemy's ship. Again, an enemy having once ascertained 
the position of such a line, could easily define the limits of 
the area of danger, and take the necessary measures to 
avoid it. These disadvantages may be overcome by spread- 
ing the mines over a certain area, so that while reducing 
the difficulties of placing in position and preserving for the 



23 

defenders a certain formation, which secures to them the 
power of identification with the more precise information 
and delicate instruments within their reach, the difficulties 
to an enemy of obtaining a definite knowledge of the area 
defended may be proportionally increased. 
The simplest method in which a system of mines can be simple distribu- 

. . tion of mines for 

arranged for the defense of a channel, is shown m Fig. 1, defense of a eban- 
which also illustrates the general principles on which they 

/ i I X I i / \ ■ '■■ .• 



c\Q ] 0; 0!\ (•):/ 0^ 



«"(. 00 © ®{r 

N / \ Fi 9 i. J" 

I / \ ' 

a \ OG )h 



© © O 0' !* 



should be arranged in all cases. In this figure a b repre- 
sents the theoretical line required to defend the channel? 
and it is only necessary to move every second mine back to 
the line e d, and every third to the line e f, to secure 
the objects required. A fourth line g h, or even a fifth , 
i 7;, may be added with advantage, taking care that these 
last shall cover the intervals left between those in advance 
of theni, in such a way that a vessel passing in obliquely 



24 

through the intervals of the first three lines, may come in 
contact with a mine in the fourth or fifth. An arrange- 
ment in lines is convenient, as giving the greatest facil- 
ities for firing at will by the method of cross-bearings? 
or for finding the position of a mine in the event of its 
becoming necessary to raise it for examination. If the lines 
are so placed as all to converge on a single distant point, 
say half a mile or more distant, the combination is much 
simplified, while the actual position of each mine is thereby 
so little altered that it may without difficulty be made to 
fulfill all the necessary conditions. The rules regulating the 
intervals to be left between adjacent charges in a line of 
mines as well as between the lines themselves shall be dis- 
cussed hereafter. 

Let us now suppose a case in which it would, from the 
depth of water, strength of currents and other conditions, 
be practicable and desirable to institute a combined system 
of defense by passive obstructions and submarine mines, as, 
for example, an estuary of a river, such as that represented 
in Fig. 2, defended by three batteries, #, y, and z. 
Defenseofa The most eligible points, which would be those where the 

channel by a com- ' 

binationofsubma- channel is narrowest, or bends where facilities exist for en- 

rine mines and . . 

passive obstruc- filading the lines ol obstructions by guns, and which would 
oifer advantages for fixing the positions of the submerged 
mines very accurately by intersections, or cross-bearings as 
they are sometimes called, and other places offering local 
advantages, having been selected, grounded obstructions 
and booms might be formed, as in the positions a a, a x a Xy in 
which openings are left in the ship-channel, to allow of free 
ingress and egress. Across these openings it would be 
necessary to place several lines of submarine mines, b b, b x Z> i? 
arranged to be fired by electricity, extending so far on each 
side of the deep or ship channel as completely to cover it, 
and well protected by the fire of the forts #, y, z, and a light 
boom, d d, might be advantageously placed in advance, to 
cover the whole system from an attack by drifting torpedoes 
or boats. The spaces c c, Ci C\ are supposed to be covered 
by a few feet of water only, and it is assumed that they 
would be sufficiently protected by the fire of the forts, and 
by guard-boats provided with proper apparatus for day and 
night signaling ; no mines are therefore proposed in connec- 
tion with them. The whole of the electrical cables in connec- 
tion with the mines should be carried into the safest avail- 
able position, if possible into the fort z : but if this is not 
practicable, those of the outer group b b might be carried 
into either of the forts x or y, and those of the inner group 
b l bi into the fort z. The necessity for placing the electrical- 



25 

room, that into which the electrical cables of any system of 
submarine mines are carried, in a safe place is very great; 
on it depends the efficiency of the whole. It would not do 
to carry the electric cables of the group hi b x into either of 

Fig, 2. (- "" 








the forts x or y, however conveniently they may be situated 
as regards the distance. They should be carried into the 
fort z, so that in the event of the forts x and y being lost, 
the space between them, covered by the group of mines, 



26 

would still remain as impassable as ever to the attacking 

ships. The electric cables in connection with the advanced 

line of mines b b might perhaps be carried into the forts x 

and y, if the distance were two great to admit of their being 

carried into the fort z $ but those of the group b x b x shoul d 

Defense of an most certainly be carried into the fort z. Fig. 3 represents 

without r p a a d s1ive another case, as, for example, an open roadstead, protected 

obstructions. ^ f 0T ^ j n w hich no passive obstructions of any sort could 

be used, but where the depth of water is not too great to 

admit of the employment of buoyant submarine mines. 

More mines would be required under such conditions, and 




they might be arranged as shown in the sketch, the same 
general rules being observed as to the situation of the 
electrical-rooms from which the whole system is governed ; 
that is to say, the cables in connection with the group b 



should be carried into either of the forts x or 
of the group b± into the fort z. 



Ui 



and those 



27 

So niueh depends upon local circumstances, such as the 
nature of the channel or roadstead to be defended, the prob- 
able means of attack at the disposal of an enemy, the 
draught of water of the vessels of a hostile fleet, &c, that 
a great deal must be left to the discretion of the officer com- 
manding the defense, and the above must not be considered 
as stereotyped plans which should never be departed from. 
They are only intended to convey a general idea of the 
arrangements necessary to meet the objects in view, which 
would require much modification to suit the specialties of 
any particular case. 



CHAPTER III. 

EXPLOSIVES. 

We now come to the consideration of the nature of the 
explosive agent with which a submarine mine can be most 
effectively charged. 

Explosive Several substances have been suggested for this purpose, 
including gunpowder, (of large and fine grain,) compressed 
gun-cotton, (fired with an ordinary and with a detonating 
fuse,) nitro-glycerine, dynamite and glyoxyline, (a new ex- 
plosive material, a combination of gun-cotton and nitro- 
glycerine, recently invented by F. Abel, esq., F. E. S., war 
department chemist.) 

Gunpowder. Gunpowder is probably the oldest and best known explo- 
sive agent that we possess. Its effects when fired in earth, 
rock, and masonry have been determined with great accu- 
racy, but we still have much to learn concerning it, when 
the surrounding substance is water. During the late civil 
war in America the confederates gave the preference to fine- 
grain or rifle-powder, under the supposition that it produced 
a better result for submarine purposes. An experiment, 
tried in a well in Pennsylvania, seems to bear out this idea. 
Captain Harding Steward, in his notes on submarine mines, 
gives the following description of the result obtained on 
that occasion : u 50 pounds of rifle-powder sent up a column of 
water 250 feet high, while, with the same charge of coarse- 
grain powder, a column of similar thickness was only driven 
70 feet high, and the water was very much discolored, prov- 
ing the non-ignition of part of the charge." 

The French seem to have got hold of the same idea, for, 
in some experiments recently carried on, they have been 
trying several varieties of gunpowder, especially manufac- 
tured with a view to obtain more rapid ignition. 

The Austrians have adopted fine-grain powder, in charges 
of 168 kilograms, or 369.6 pounds, in some of their most im- 
proved forms of apparatus. 

a strong case It is probable, however, that when gunpowder is used, 
gTnpowd'e/is the strength of case is of more importance than the consid- 
eration as to whether coarse or fine-grain powder should be 
employed. A case of sufficient strength to secure a proper 
development of the explosive force of the charge, would be 
likely to produce a greater increase in that force than would 



29 

result from a change in the form of powder of which the 
charge is composed. The experiments made by the float- 
ing-obstruction committee seem to prove this to be the fact. 

As regards compressed gun-cotton we are somewhat in compressed gun- 

« r o cotton. 

the dark ; but a great number of experiments have been 
recently made with this substance, fired with an ordinary 
as well as with a detonating fuse, which throw much light 
on the subject, and from which its effects, as compared with 
those of proportionate charges of gunpowder, have been 
approximately determined. 

The results obtained from these seem to show a superior- 
ity, under certain conditions, for gun-cotton over gunpowder 
for submarine work; its ignition, at all times more rapid 
than that of gunpowder, is, when fired with a detonating 
fuse, immensely quickened, and the damaging effect of its 
explosion is much increased, both of which properties are 
in its favor.* 

It is to be remarked that the Austrians, who originally 
used gun-cotton in their submarine mines, appear to have 
given it up, in consequence of the difficulty they experienced 
in manufacturing it of uniform strength, and the danger of 
spontaneous explosion. Mr. Abel's process of making it in Abel . s i mpr0 ve- 
a pulp seems to get over these difficulties. He has identi- Sure tf 6 gun- 
ned himself with the advancement of the gun-cotton ques- cotton - 
tion, and great credit is due to him for the light he has 
thrown upon that question by long and patient experimental 
research. Still greater credit is due to him for haviug dis- 
covered and perfected a method of treating gun-cotton, 
whereby it is rendered non-explosive when burned in the 
air, but in which the full energy is developed when fired in 
a close chamber, or with a detonating fuse. The method 
consists in reducing the gun-cotton fiber to a fine state of 
division or pulp, as in the process of paper-making, and in 
converting this pulp into solid masses, of any suitable form 
or density, under a pressure of 18 tons to the square inch. 

* Mr. Abel, who has investigated the action of detonating fuses in 
developing the explosive power of nitro-glycerine and gun-cotton, states 
that gunpowder, or any other explosive agent, may he made to exert its 
full explosive force when only confined in a weak case, or bag, or even 
when exposed to the air, by being fired through the agency of a sudden 
and sharp concussion, such as that produced by the explosion of a con- 
fined charge of fulminate of mercury. He states that the explosion of 
powder, by means of a detonating fuse, is decidedly sharper or more 
rapid than that produced by firing it in a strong receptacle in the ordi. 
nary way. Some recent experiments have indicated that more work can 
be got out of a combined charge of powder by this means than by its 
explosion in the ordinary manner, under corresponding circumstances. 



30 

This method of manufacture is now carried out by Messrs. 
Prentice, at their works at Stowmarket. To the pulping is 
mainly due the safet} 7 attained, as it insures uniformity in 
washing, whereby, the cotton is thoroughly freed from all 
acid, and thus every chance of spontaneous combustion is 
removed. The compression causes combustion to proceed 
slowly in the open air, owing to the condensed condition of 
the fibers, which, in the loose state of cotton or rope, burn 
very rapidly. Tiie gun-cotton is compressed into cylindrica I 
or any other convenient forms, and a density equal to that 
of powder is given to it, whereby its portability and the 
explosive force of a given volume are greatly increased. 
The principle of thus combining safety with force, in a 
highly condensed form, has produced very valuable results. 
Before any definite opinion can, however, be pronounced 
on this substance as an explosive agent, it is necessary to 
try some further experiments with large charges. The effect 
of compressed gun-cotton, fired with a detonating fuse, is 
marvelous. The power possessed by a detonation of de- 
veloping suddenly the full explosive force of gun-cotton 
was discovered by Mr. Brown, of the chemical department, 
Woolwich ; and several forms of detonating fuses, to be 
fired either by electrical agency or by means of Bickford's 
fuse, have been constructed by Messrs. Abel & Brown. 
The electric detonator is a modification of Abel's fuse, a 
charge of fulminate of mercury being substituted for the 
powder priming, and the wooden fuse-case being strength- ■ 
ened by an outer tin case, which assists in developing the 
Experiments detonating power of the fulminator. The following sum- 
Tnd lyoxyiine! mary o f the result of some experiments carried on with it 
foniiugftui de an( * w ith glyoxyline, under the auspices of the royal engineer 
committee, at Chatham, on the 6th August, 1868, give an 
idea of the effect produced : 

Experiments were first made to show that neither of these 
substances, compressed gun-cotton and glyoxyline, will ex- 
plode when unconfined and merely fired with an ordinary 
fuse, either time or electric, but that they require a detona- 
ting fuse to explode them under such conditions. 

These experiments were most successful ; the gun-cotton 
when ignited with the ordinary fuse only burning, and the 
glyoxyline being simply blown about without ignition. 
When the detonating fuse was used, the charges being still 
unconfined, both substances exploded with great violence, 
disintegrating the pieces of wood on which they were placed. 
Five charges were fired successively against a stockade, 
formed of 1 foot 2 inches square timbers, placed close to- 



31 

getker and firmly planted in the ground. The piles were 
chiefly of pine, except those specified to the contrary. The 
following is the result : 

1st. Five pounds of glyoxyline hung in a bag about two 
feet from the grouud. This blew in a hble about one foot 
in diameter, resembling the effect that would have been 
produced if a round shot had passed through. Half the 
timber above the point of explosion was also carried away 

2d. Ten pounds of glyoxyiine hung in a bag about two 
feet above the grouud. This produces just double the effect 
of five pounds, the whole of the timber above the point of 
suspension being carried away. 

3d. Ten pounds of compressed gun-cotton laid along the 
foot of tbree piles. This cut a clean gap through two whole 
piles and half the third. 

4th. Ten pounds of glyoxyline laid in a train against three 
timbers, two of oak and one of pine. This cut through all 
three. 

5th. Five pounds ten ounces of glyoxyline and five pounds 
of compressed gun-cotton. Each charge laid along the 
ground against three and a half piles, and consequently 
covering a space of seven piles altogether. The piles were 
cut half through, with the exception of one which was split 
completely through, though not severed. The line cut was 
three or four inches wide. 

A plank being lowered over the counter-scarp of St. Mary's e x P e r i m e n t 
front, to a depth of 10 feet, the total height being 18 feet, Sp S of COU sahn 
the following charges were placed on it : 20 pounds of gly- Mary 
oxyline were laid along 3 feet of plank, and 20 pounds of 
gun-cotton along 3 feet more by its side. The explosion 
was extremely sharp, and a partial breach of the following 
dimensions was formed: 7 feet high, 11 feet wide, and 20 
inches in depth. The brick- work was very much shaken for 
some feet on either side of breach, and pulverized for some 
inches more in depth. 

From these experiments it is probable that these sub- Result oi expei 
stances may prove exceedingly valuable for making breaches iments - 
in timber and masonry, when portability and rapidity of 
action is required, 'as, for example, to breach a stockade or 
form a lodgment in the revetment of a work. Tamping 
may be dispensed with, which is a great advantage ; but it 
must be borne in mind that, in order to produce a maximum 
of effect, absolute contact with the object to b.e destroyed 
is necessary, and for this purpose it would be convenient to 
prepare the charges beforehand, by placing them in bags or 
tin cases of suitable form, generally cylindrical and very 



32 

long as compared to their diameter, so as to cover any 
space required. 

Some further experiments were tried on the 5th Sep- 
tember, 1868, against the same stockade. The breaches 
formerly made had been repaired, but certain alterations 
were introduced in its construction, viz, no earth was raised 
against the outside, the ground being level there ; this earth 
was moved inside, and, together with blocks of granite, iron 
guns, and railway iron, was used to strut up the timbers 
and strengthen the stockade in the interior. 

1st. Five pounds of compressed gun-cotton in disks were 
laid on the ground outside, against one of the logs, (of fir,) 
forming the stockade. This log was 13 inches square, and 
was strengthened behind by a block of granite, weighing 9 
cwt., and earth. It was also secured to the adjoining logs 
by a ribbon with 7-inch nails. This charge, fired with a 
detonating fuse, cut through three-fourths of the log at the 
foot and forced the block of granite behind 1 foot 6 inches 
to the rear. 

It was the opinion by those present that the ribbon alone 
prevented the log from falling. 

2d. Seven and a half pounds of gun-cotton were now tried 
under similar circumstances, as in the first experiment, 
against a log of fir, 14 inches square. This log was only 
strengthened behind with earth 3 feet 6 inches high by 4 
feet at base. The log was cut through and fell forward, the 
cut end being buried in the earth behind. 

3d. Seven and a half pounds of gun-cotton were placed 
equally on both sides of a corner log (of fir, 15 inches square) 
of the stockade. This log was powerfully supported on the 
other two sides by those adjacent to it, forming the stockade. 
It was cut clean through and the bottom driven out 3 feet, 
the log leaning in this position against the others. 

4th. Seven and a half pounds of glyoxyline were placed 
loose on the ground against one log of fir 13 inches square, 
supported behind by small blocks of granite and earth 3 feet 
high by 4 feet at base. The log was cut completely through 
but remained standing, the top leaning forward about 2 
feet beyond those adjacent to it. The effects of this glyoxyline 
charge were not so local as those of gun-cotton. With gun- 
cotton the adjacent logs were not touched; with this charge 
of glyoxyline, however, the two adjoining k logs were much 
splintered. This difference of effect, between gun-cotton 
and glyxoxline, was probably due to the different manner 
in which the two materials were piled against the logs. 
The cotton, being in disks, was packed close up against the 



33 

logs. The glyoxyline, being in pellets, was piled loosely 
against the logs, and therefore the center of gravity was not 
so close to the logs as in the case of the gun-cotton. It also 
fell over a little again t the adjoining logs. 

5th. A tin cylinder, 3J inches in diameter, and 3 feet G 
inches long, was loaded with 10 pounds of gun-cotton in 
disks, which, to lengthen the charge, were separated by £- 
inch milled board. The cylinder was laid'against three fir- 
wood logs, 14 inches square each, and which were supported 
behind by two 18-pounder iron guns and two pieces of rail- 
way iron, besides being secured to another by ribbons 
of wood and iron dogs. This charge was fired with a 
Bickford's fuse, at the end of which was a detonating 
arrangement. The explosion, which was very violent, over- 
threw the two left-hand logs, which fell forward, and very 
nearly severed the right one at the base, which, however? 
remained standing, being prevented from falling by the 
ribbons and dogs securing it to the adjoining logs. 

This concluded the experiments against the stockade. 

6th. The gun-cotton disks were now tried against some 
palisades near the stockade. Four disks, weighing 4 ounces 
each, were placed one under each of four adjacent palisades, 
their edges being 9J inches apart. One of the outer disks 
was then fired, in order to see whether the explosion would 
ignite those adjoining it. This did not occur ; only one was 
exploded, which cut the palisade against which it was 
placed clean off level with the ground, but hardly even 
disturbed the adjoining disks. 

In order to test the effects of these explosives on beams Experiment* o«» 

. beams of timber 

or timber, some experiments were made on a wooden sta- with gun-cotton 

-••« a n ■»» and detonating 

gmg in the ditch, to the west of St. Mary's horn - work. fuse. 
The timber was of fir, but very old and full of shakes. 

One of the beams, 10 inches square, composing the sta- 
ging, was bored with a vertical hole 1J inches in diameter, 
into which 2 ounces of gun-cotton was put. This charge 
completely severed the beam and split it, in several places, 
to a distance of 3 or 4 feet from the charge. 

One ounce of gun-cotton was now tried under similar 
circumstances. This shattered the beam considerably, and 
split it so that it could be seen through, but did not sever it. 

Large splinters of wood were thrown by these explosions 
to distances of as much as 20 yards. 

A single disk of gun-cotton, weighing 1 pound 2 ounces, Experiment « 
was now placed on the top of a block of granite 3 feet 9 with gun Son 
inches by 2 feet 9 inches and 2 feet deep. The block of !£* detonating 
granite had had several jumper-holes bored in it, which 
3 



34 

bad, however, been tamped up again, but must have weak 
ened it considerably. The result of this explosion was that 
the block of granite was split vertically all around at an 
average distance of 2 inches from the outer edges, besides 
having a hole 1J inches deep scooped out in the top of it at 
the seat of the charge. It was also much shaken, and could 
easily have been picked to pieces. The result of the frac- 
ture around the stone was that, in a few days, the part 
split scaled off and fell away from the block. 

The whole of these experiments would seem to prove that 
gun-cotton, prepared according to Mr. Abel's method and 
fired by a detonating fuse, is quite as powerful in its action, 
if not more so, than the mixture of gun-cotton and nitro- 
glycerine, called glyoxyline. 

The average price of the two would be about equal, being 
(according to Mr. Abel) 20d. per pound weight, or 2J times 
the price of blasting-powder j but as the effects of one pound 
of gun-cotton for these purposes appear to be equal to those 
of 4 pounds of gunpowder, it would in reality be 38 per cent- 
cheaper to employ gun-cotton. The specific gravity of com- 
pressed gun-cotton is the same as that of gunpowder $ that 
of glyoxyline one-third less. 

Gun-cotton is more liable to absorb moisture tban glyox- 
yline, though it is not permanently injured thereby. The 
transportation of nitro-glycerine dissolved in wood spirits, 
for the manufacture of the latter, is troublesome and expen- 
sive and, unless carried about in this way, nitro glycerine 
is very dangerous to move, whereas gun-cotton is not so. 
For actual service, however, the glyoxyline would be man- 
ufactured beforehand, and the masses, (grains, disks, &c.,) 
would be coated with an impervious varnish, which would 
effectually inclose the nitroglycerine and protect the pre- 
paration from the atmosphere. 
Effect of com- The effects of these explosives are so powerfully concen- 

■pressedgun-cotton 

fired, under water, trated and local, that it can hardly be doubled but that, if 

fuse. ' sufficient quantities were used, iron plates of considerable 

thickness could be pierced by them, especially under water. 

A few charges of compressed gun-cotton have also been 
fired, with a detonating fuse, under water with the following 
result : 

1st. A charge of 3 pounds J ounce was fired at our experi- 
mental target, (the squares of which are of fir, 14 inches square 
and 1 inch thick,) at a distance of 20. feet from the target and 
with 7 feet six inches immersion ; this broke 22 squares. 

2d. Three pounds Of ounce, 30 feet distant from the target, 
and with 7 feet G inches immersion broke 10 squares. 



Twenty pounds of powder, at a distance of 20 feet, pro- 
duced less result than this charge of gun-cotton at 30 feet. 

With both these experiments the shock experienced was 
most violent. The sprats and small whiting, for a consid- 
erable distance above the point of the explosion, were killed 
and drifted past in great numbers. 

The above two experiments were made to test the com- 
parative strength of the explosion of gunpowder and its 
equivalent of gun-cotton. 

3d. Charges of 15 pounds of powder and 3 J of gun-cotton Comparative ef- 

feet of powder 

were placed on the mud and fired at high water, at a depth and gun - cotton 
of 10 feet. The charges were fired together, and the columns ting 'fuse, under 
of water were observed to be about equal, but more mud bottom? 11 a 
was intermixed into the column of water thrown up by the 
powder. 

The craters were examined at low water, when they were 
high and dry. 

Each crater was found to be 9 feet in diameter, the gun- 
cotton crater was 2 feet deep, and the gunpowder crater 
4 feet deep. 

It would appear from this that the shock of the gun-cot- 
ton explosion only compressed the mud in a downward 
direction, and the mud so compressed afterward recovered 
to a certain extent its original position. 

In the gunpowder crater the mud was less violently but more 
thoroughly thrust aside, and thus a deeper hole was made. 

The lateral effect, which was really what we wanted to 
arrive at, was about equal, the charges of powder and 
gun-cotton being as 1 to 1. 

Against an air-backing, which, would be the condition 
presented by a ship's side, a decided superiority for the gun- 
cotton is shown in the first and second experiments. 

Before any definite conclusions can be arrived at, exper- 
iments on a larger scale must be undertaken. It may, 
however, be laid down as an established fact that the local 
action produced by a charge of gun-cotton, ignited by a 
detonating fuse, is enormous; that this effect is quite inde- 
pendent of tamping, except in loose or soft material, such 
as earth, and that the instautaneous explosion produced is 
in no way affected by a want of absolute contact or by a 
small interval between the disks, rings, or masses composing 
the charge, as shown by the fifth experiment of the 5th 
September, 1868; or, in other words, that no compression is 
required at the moment of ignition. This in submarine 
mining is a very great point gained, as it does away with 
the necessity for considering the strength of case, as far as 



36 

tlie development of the explosive force is concerned ; a 
thoroughly water-tight envelope, of sufficient strength to 
resist the pressure of the water at the depth to which it is 
required to be submerged, being alone required. The cer- 
tainty of immense local action being, as already stated, es- 
tablished, it only remains to be proved that the radius of 
destructive effect is at any rate equal, with equal weights, 
to gunpowder, to relieve us from many difficulties to which 
submarine explosions are at present liable, and it is to be 
hoped that this very desirable result may be arrived at. 
Relative values In a very carefully written article which appears in " En- 
gun- cotton, and gineering" of the 12th February, 1869, the relative mechan- 
examined theoretical forces generated by the explosion of gunpowder, gun- 
"f.'ii v. a ' '" cotton, and nitro- glycerine have been determined theoretically 
and chemically, the pressure of the atmosphere being taken 
at 15 pounds on the square inch, to be as follows: 1 grain 
of gunpowder, when fired, produces a pressure of 200 
pounds on the square inch ; 1 grain of gun-cotton pro- 
duces a pressure of 1,204 pounds on the square inch f and 
1 grain of nitro-glycerine produces a pressure of 1,1G7 
pounds on the square inch. 

It is probable that these values are not far from the truth, 
provided the explosion takes place under exceptionally favor- 
able circumstances as to strength of case and completeness 
and rapidity of ignition, but such conditions would very 
rarely occur in practice. 
a maximum of Perhaps the nearest approach to such perfection of igni- 
obtajned by firing tion is obtained in the case of gun-cotton or glyoxyline, and 
detonating Sie! a also with gunpowder, fired with a detonating fuse; and if 
this theory is true, we may assume that the explosive effect 
of a charge of either of these substances, when fired with 
this particular form of fuse under favorable conditions, ap- 
proaches very nearly to a maximum, or, in other words, to 
the effect which would be produced by the same charge 
fired with an ordinary fuse, and contained in a case, the 
strength of which had been calculated to a nicety, so as 
just to exert the proper pressure to develop the maximum 
force at the moment of ignition, and yet not so strong as in 
the smallest degree to reduce that force by the pressure re- 
quired to burst too strong a case. 
Gun-cotton non- One great advantage of gun-cotton is that, if ignited in 
«xpio S1 ve when a ^ ee Q ^ Qn S p ace? ft simply burns without explosion, and 
that, in order to render it incombustible, it is only necessary 

* This result is based on data derived from the forms of gun-cotton 
originally manufactured as to density and consequent weight, viz, 11 
pounds to the cubic foot. Compressed gun-cotton weighs considerably 
more; nearly as much as gunpowder. 



Nitro-srlyccriin 



37 

to wet it. This wetting does not injure it in the least degree, 
and when dried again it is as good as ever. A drowned 
charge may consequently be restored to a perfectly efficient 
state. This property, together with the greater security for 
storage and manipulation consequent theron, gives it a 
great advantage over gunpowder. 

Toward the close of the late civil war in the United States, 
a good deal of gun-cotton was sent out to the confederates, 
but it does not appear to have ever been used by tuein. 

The third explosive alluded to is nitro glycerine. Some 
experiments, with a view to testing its capabilities for sub- 
marine work, were made by the United States Government, 
but with what result I am unable to say. Our experience 
of it, derived from experiments made at Chatham, is, ho.v- 
ever, such as to lead us to discard it for the above purpose. 
Its advantages are the very compact form in which charges 
might be arranged, its greater explosive effect, weight for 
weight, as compared with gunpowder, six of powder being 
about equivalent to one of nitroglycerine, the peculiarly 
damagiug effect of its explosion, and that leakage of water 
does not prevent its ignition; but it is extremely dangerous 
to store, and its effects upon those working with it seem 
prejudicial to health. Further, it seems to require much 
care in arranging the charge for ignition, and we found 
that, unless confined in a strong vessel, such as a shell, for 
instance, there was no certainty that it would be fired by 
an Abel's fuse, specially prepared for the purpose ; it seems 
to require a large amount of compression, or to be submit- 
ted to concussion the moment of ignition. This latter fail- 
ing might possibly be got over, but its other disadvantages 
are quite sufficient to condemn it as an explosive agent for 
submarine mines. 

Another substance which might be used for submarine Dynamite, 
mining purposes is " dynamite." This may be described 
as a mixture of nitroglycerine and silica, by which the for- 
mer is said to be made as safe to handle as ordinary gun- 
powder. Its discovery is due to Mr. Kobel, a German engi- 
neer. The question of safety in carrying, storing, and 
manipulating this substance, requires further testing ; if it 
is simply a painting over, as it were, of the particles oi 
silica, it is possible that the shaking necessarily encountered 
in carriage, or even long storage, might have the effect of 
settling or running the nitro-glycerine together, under which 
circumstances it would become as dangerous as nitro-gly- 
cerine unmixed. The following experiments with submarine 



38 

mines filled with dynamite, made in September, 1868, at 
Carlskrona, Sweden, give some idea of its effects : 
Experiments The target was the hull of a 60-gun frigate, which had 
againg/iran 11 ^ a been built in 1844; her timbers and planking were quite 
caSrona gate at sound ; timbers of oak, about 13 inches square, 1 inch 
apart ; planking of Swedish pine, 5J inches ; bottom strength- 
ened inside with wrought-iron diagonal bands, 6 inches by 
1J inches ; inside planking running half way up to the bat- 
tery deck of oak, 6 inches thick. The hull had been "raze" 
down to the battery-deck, and the copper removed. The 
chief object was to ascertain the effect of dynamite, in a 
contact-mine, against a strong wooden vessel, as well as 
against a double-bottomed iron vessel ; and, with this object 
in view, a quadrangular opening had been effected on the 
port side and filled with a construction representing a 
strong double iron bottom, firmly fastened to an oaken frame 
that had been put on inside, on the four sides of the open- 
ing, and with through-going bolts, 1 inch in diameter, to 
the timbers. The mines were arranged as follows : 

Starboard side No. 1, about amidship, 7 feet below water- 
line, with the center of the mine 2 feet 2 inches from the 
bottom of the ship; charge, 13 pounds of dynamite in a 
thin iron case, (jL-inch plate.) The mines, although repre- 
senting contact- mines, were placed some little distance from 
the ship, on the supposition that they would or might be 
pushed to some distance away from the striking ship before 
they exploded. 

No. 2. About 40 feet from stern, 7§ feet below the water- 
line, center of mine, 3 feet from the bottom of the ship ; 
charge, 16 pounds of dynamite in a glass vessel. 

Port side No. 1. About 30 feet from the stern, 5f feet 
below the water-line, 2 feet from the ship's bottom; charge 
16 pounds of dynamite in an iron case of yL-inch plate. 

No. 2. About 40 feet from No. 1, 6 J feet below the water- 
line, 2 feet 2 inches from the ship's bottom; charge, 10 
pounds of dynamite in a case as above. 

No. 3. 2 ieet 2 inches from the center of the iron bottom, 
7 feet 4 inches below the water-line ; charge, 13 pounds of 
dynamite in a case as above. 

These five mines were fired at the same moment, the hull 
was lifted about a foot, and sunk in 1J minutes. 

The wreck having been docked, the effect of the different 
mines were found to be as follows : 
Effect of the Starboard No. 1. Timbers broken and thrown inside, into 
the hold, on a space of about 15 feet by 8 feet, leaving a 
hole of those dimensions; three more timbers on one side of 



mine 



39 

the hole broken; inside oak planking rent oft' on a length of 
14 feet; two iron bands torn up and bent, one of them broken 
in two plaees ; outside planking off on a space of about 21 
feet by 12 feet ; several planks, still higher up, brokeu. 

No. 2. Timbers blown away on a space of about 8 feet 
square; inside planking off on a length of 20 feet; two iron 
bands broken, and torn up and bent; outside planking off 
on a space of abont 19 feet by 12 feet. 

Port side No. 1. Timbers blown away on a space 10 feet 
6 inches by 12 feet at one end, and 6 feet at the other; inside 
planking off for a length of 14 feet ; one iron band torn up, 
one broken ; outside planking off on a space of 18 feet by 
25 feet and 15 feet. 

No. 2. Timbers blown away on a space 4 feet in length 
and 16 feet in height; on the sides of this hole, 10 timbers 
were broken; two iron bands torn up, one broken; inside 
planking off for a length of about 20 feet; outside planking 
off for a space of about 20 feet and 23 feet by 10 feet and 13 
feet. 

No. 3. The gas sphere had hit the middle of the outside 
plates on one of the angle-iron ribs. This rib was torn from 
the timbers and bent up, nearly two feet in the middle, but 
not broken. There was an oval hole in the outside plates 
4 feet by 3 feet between two ribs, which ribs, with the 
plates on edge riveted to them, were bulged out about 5 
inches. The inner plate, one large piece, was blown up in 
a vertical position, after having cut all the bolts and rivets, 
60 of 1 inch, and 30 of f inch, save those that fastened the 
lower side to the oaken frame and timbers. On a length of 
about 30 feet and height of about 20 feet the bottom, on all 
sides of the iron construction, had been bent inwards ; the 
greatest bend was about 5 inches; three deck-beams above 
had been broken. 

By the joint effect of all the mines, almost all the iron 
deck-beam knees had been rent from the side, and there 
was an opening between deck and hull on both sides for a 
length of about 130 feet. 

The last and newest explosive agent is glyoxyline, recently Giyoxyiine 
invented by Mr. Abel, chemist to the war department- 
This is a compound of gun-cotton and nitro glycerine, pre" 
pared by soaking the former, in a granulated state, or in the 
form of disks or pellets, in the latter, of which it will take- 
up nearly its own weight; the masses are then coated with 
a varnish, which perfectly excludes air and incloses the 
nitroglycerine; when thus manufactured, it is said to be 
as sate to handle as ordinary gunpowder. Its explosive 



40 

effect, when fired with a detonating fuse, is very similar to 
that of gun-cotton fired with the same fuse, and as the latter 
is very much safer to handle, it is consequently greatly to 
be preferred, unless future experiments develop any pecu- 
liar advantages to be derived from the use of glyxoyline. 

It is of importance to keep in view the necessity of using 
an explosive substance for submarine, or indeed for any min- 
ing jmrposes, which, though powerful in its effects when 
•required to act, and of a nature suitable to the work to be 
done, may yet be safely stored and manipulated when ordi- 
nary care is used ; and we may on this account at once put 
aside the many compounds which, though at first sight pre- 
senting advantages, are liable to explode unless handled 
with extreme care. Picrate of potassium is an example of 
this class, and the fearful explosion of this substance which 
recently occurred in Paris, is enough to condemn it. 

size of charge. The next point to be considered is the amount of the 
charge, of powder or other explosive, to be employed in each 
mine. On this subject we have still a good deal to learn, 
and, before we can bring the calculation of charges for sub- 
marine mines to the same degree of certainty which has 
been attained as regards those for ordinary earth, rock, or 
masonry, much remains to be done. 

The points to be determined are the depth at which a 
given charge is most effective; the lateral and vertical 
range at which a certain charge may be relied on to pro- 
duce a given result, and what that result would be on the 
bottom of a vessel as strongly built as a modern ship of 
war. 

Experience o f The experience of the confederates on th is point is described 

confederates on 

size of charge. by Captain Harding Steward, R. E., in his notes on sub- 
marine mines, as follows : " With submerged torpedoes, as 
employed by the confederates, the regulation of the charge 
depended on the depth of water, the nature of the bottom, 
and structure of the ships to be expected, except in the 
case of small torpedoes, moored a little below the surface 
and arranged for contact. With these the proximity of 
the charge to the object altered the conditions. The fol- 
lowing scale of charges, suitable to depths from two 
fathoms and upwards, was made for use in the James 
Eiver, where the bottom is very soft. It is based on data 
obtained from the destruction of wooden vessels of 800 
tons, by the confederates; also from experiments, and is 
suitable to strongly built wooden vessels up to 1,000 tons : 
charges for a 2 fathoms - 300 pounds of powder. 

i ? ooo-tcn vessel. 3 fathoms . - - > 000 pounds of powder. 



41 

4 fathoms 900 pounds of powder. 

5 fathoms 1, 200 pounds of powder. 

6 fathoms 1, 500 pounds of powder. 

7 fathoms 1, 800 pounds of powder. 

8 fathoms 2, 400 pounds of powder. 

With hard bottoms the charges eould be diminished, for smaller charges 

, „ n , T ,, j? i for a hard bottom . 

the waste of powder is not so great. In the case ot a rocky 
bottom, as much as 25 per cent, may be deducted, accord- 
ing to the American experiments, because the rebound of 
the portion of the gas that acts downward is almost coinci- 
dent with the upstroke of the rest. These charges, even 
considering the objects in view, appear excessive, but it 
must be remembered that the confederates used only one 
fuse for ignition. With a proper arrangement for igniting 
the charges at several points a reduction might have been 
made amounting to 40 per cent. As I have before men- 
tioned, the employment of large charges was made with 
a view of controlling a large area, and destroying the ves- 
sel through the commotion of the water, when beyond the 
direct action of the charge. This plan may be a good one 
with small vessels; but the worst feature of the system is 
the fact that, as in some cases, the result depends upon 
the lifting powers of the charge, the quantity of powder 
must necessarily be increased in proportion to the size of 
the vessels expected. A progressive increase of one third charges in- 
of the amount given in the foregoing scale, for every extra vessels. 
thousand tons of measurement, was considered by the offi- 
cer superintending the mining operations in the South as 
the least that could be done in the case of large vessels. 
This is no doubt true, but with vessels of 3,000 to 4,000 
tons it brings the charges to quantities too large for proper 
arrangement." 

As regards this scale of charges recommended by the 
confederates, it seems to be somewhat fallacious to go on 
increasing the charges without limit, according to the depth, 
and we may therefore safely assume some point beyond . 
which the charges should not be increased. Probably 2,000 
pounds might for the present be assumed as a maximum, 
which ought to be sufficient to break the bottom of any 
vessel, however strongly she may be built, if fired in a proper 
position with reference to her. As the tonnage of a vessel 
increases, so generally does her strength ; but so also does 
her draught of water, and, consequent upon the latter fact? 
if the charges were always kept as deep as possible, a larger 
vessel would always find a larger charge in proportion to 
her size, in close proximity to her, wherever there was suffi- 



42 

cient water to allow her to pass. On the contrary the large- 
charge would probably reach a smaller vessel, and as effect- 
ually damage her notwithstanding the cushion of water in- 
tervening. 

In the sixteenth volume of the Professional Papers of the 
Corps of Eoyal Engineers, a description is given by Lieu- 
tenant W. A. J. Wallace, E. E., of the means adopted for 
blowing up some wrecks of vessels in the river Hoogly. 
Lieutenant Wallace's conclusions as to the size of the charges 
to be most advantageously employed, as derived from these 
experiments, are as follows : 
size ot charges « The size of the charges when they cannot be placed 

used in destruc- .... -,. . . . ., . 

tion of wrecks m inside or under the wreck should, in my opinion, be regu- 
lated by the depth of the water. In from four to nine fathoms, 
450 and 500 pound charges were found to answer very well, 
but I think they might have been increased with advantage 
at the latter depth. 

"Between three and four fathoms, 250 and 300 pound 
charges are generally the most economical j a larger quan- 
tity simply throws the water to a greater height without 
producing a corresponding increase in destructive effect." 

It is to be remarked, however, that these charges were, in 
every case, arranged to be in actual contact with the 
vessel, and were intended simply to break up the wreck in 
such a way as to clear the channel, and, especially at the 
greater depths, they would be found much too small for use 
as submarine mines, 
charges m con- The charges used by the confederates in their drifting 
t e o d rp a e e d e r s ft to? torpedoes were usually about 100 pounds of powder, and 
small. were productive of comparatively small results ; thisis in a 

great measure accounted for by the fact of their explosion 
occurring at, or very near, the surface of the water. The 
charges they employed in the attack of vessels with their 
torpedo boats were 50 pounds of powder, which proved in- 
effective in many cases, and I think may be pronounced 
too small for the purpose required. 
Experiments A great number of experiments have been made at 

made at Chatham . ■ . . . 

for floating ob- Chatham for the floating obstruction committee, with a view 

struction commit- . . 

tee. to determine the depth at which a given charge is most 

effective, as well as the radius of explosive effect, or dis- 
tance from such charge at which a vessel would be destroyed. 
This series is not yet completed, as it will be necessary to 
fire some larger charges than those with which experiments 
have hitherto been made. The results as yet obtained give 
us the following information, which, though it can only be 
regarded as approximately true, must be our guide until the 



43 

subject is further investigated : first, that 100 pounds of 
powder is most effective at a depth of 10 feet — that is to 
say, that as it approaches nearer to the surface much of its 
energy is lost by the escape of the gas toward the air, and 
the lateral effect is reduced proportionally. Actually on 
the surface the lateral force of explosion would be at a min- 
imum, which would in a great measure account for the 
small amount of damage caused by the confederate 100- 
pound charges in the mechanical contrivances already al- 
luded to. Again, if the charge be lowered the explosive 
effect seems to be smothered, so to speak, by the increased 
pressure of the water and the lateral effect consequently 
diminished. When further experiments have been made 
the depth at which larger charges are most effective will be 
determined ; secondly, from the observation of the results Radius of expio- 
of certain experiments made with charges of known sizes, 
fired on the bottom with different superincumbent depths 
of water, it has been found that when a charge is immersed 
to that depth at which it is most effective the radius of 
explosive effect may be derived from the equation 

where K = radius of explosive effect in feet, and c the charge 
of gunpowder in pounds. Where gun-cotton fired with an 
ordinary fuse is used, the value of c would have to be mul- 
tiplied by 4 and the equation would stand thus : 



sive effect. 



E = ^32 c, 
and so on for any other explosive substance used, the pro- 
portionate effect as compared with gunpowder having been 
obtained. The relations expressed in this equation are 
completely borne out by the result of an Austrian experi- 
ment on a large scale, in which precisely the same effect 
was obtained, in proportion to the size of the charge em- 
ployed. 

When the results of the larger charges have been obtained, 
it is possible that the deductions arrived at may be some- 
whac modified, but in the mean time they seem to be suffi- 
ciently near the mark to be adopted for any calculations 
we may have to make. 

In an experiment tried at Chatham on Her Majesty's ship Experiment on 
Terpsichore, a charge of 150 pounds of fine-grain rifle-pow- Terpsichore, 
der, placed in 22 feet of water, on the bottom of the river 
Medway, at a distance of 12 feet below the keel of the ves- 
sel and 2 feet horizontally clear of the side, made a hole at 
a distance of 19 feet, in a direct line, and nearly in a vertical 
direction, of such a size as to sink the ship in a few minutes. 



44 

We learn from the result of this experiment that the ex- 
plosive force of a charge acts most strongly, whatever the 
depth may be at which it is submerged, in the direction of 
the line of least resistance, which in this case was through 
the bottom of the vessel, precisely at the point where the 
charge broke through. 
Experiments on In the spring of 1866, a number of experiments were tried 
America! 8 y b ip at Portsmouth, by firing several charges of various sizes, 
suspended at different horizontal distances from the sides 
of Her Majesty's ship America, and at different depths 
of water. No very decisive results were obtained from these 
experiments, but the fact that the destructive effect of 
charges, in a horizontal direction, diminishes rapidly as the 
distance increases is to be remarked. 
von scheiiha's In his Treatise on Coast Defense, recently published, 

experiments. ' ti i > i • ±_ 

Colonel Van iSchehha gives the result of several experiments 
which he made himself. Some of these results are very 
anomalous, and do not at all bear out preconceived notions. 
They, however, confirm the idea, of which there can be now 
no doubt, that the explosive effect of a charge acts most 
strongly in the direction of the surface, or line of least re- 
sistance, whatever may be the depth of the water. 
General conciu- The destructive effect would appear to be limited to the 

sions as to the ef- . 

feet of a charge area from which the gas of the exploded charge drives 
* away the water. The first effect of the explosion would be 
the formation of a globe of gas, exerting a pressure equal 
in all directions. Water being practically incompressible, 
the effect in the direction of the sides is a force which is 
instantly communicated horizontally through the water as 
a shock, for a considerable distance; but in consequence of 
the ready transmission of this shock, in all directions hori- 
zontally, there is but little damaging effect. The effect of 
the gas in a vertical direction, is no doubt much enlmnced 
by its very low specific gravity as compared with water, 
but its expansion, originally due to the great heat which 
caused its production, is immediately checked by the cool- 
ing influence of the surrounding water. The gas then, in 
the first instance, would appear to lift bodily a column of 
water immediately overlying the primary globe of explo- 
sion ; as soon as this column of water is set in motion the 
gas commences to force itself through it, and we have a 
column of spray, or a mechanical mixture of gas and water, 
ejected above the surface of the water. In the event of a 
ship being immediately over the charge, if the strength of 
her timbers w T ere greater than the resistance of the depth 
of w T ater on each side, the line of least resistance would evi- 



45 

dently be to the right and left of the vessel, and the great- 
est effect of that charge would be just clear of the ship's 
sides. But, as in the majority of cases, when a charge is 
exploded near the bottom of a ship, the resistance of the 
timbers against an upward blow would be less than that 
of a column of 18 or 20 feet of water ; it would take effect 
in that line of least resistance, or through the ship ; in such 
a case there would probably be no indication of an explosion 
on each side of the ship, except a slight disturbance on the 
surface of the water. In this case the water in all directions 
except between the charge and the ship, acts as a most 
sufficient tamping, or an incompressible medium. That 
this water-tamping is most effectual would be best exempli-, 
tied by first exploding a charge placed on the surface of the 
water against a ship's side, noting the effect, and then ex- 
ploding a similar charge against the ship's side, but im- 
mersed 10 or 15 feet. In the first case, however, the explo- 
sive effect of the powder would be in one respect greater, 
owing to the absence of cooling of the gas, the explosion 
being principally in air. The difference of strength in the 
side of a ship at the water-line and 10 feet below the water- 
line, must, in such an experiment, be taken into consider- 
ation, as it is presumed that in a modern ship of war, a 
greater strength will always be provided at the water-line 
than under the quarter. 

There is an additional amount of water ejected in the ex- 
plosion of a submarine mine, due to the pressure of the 
atmosphere forcing the surrounding water to fill up the 
vacuum caused by the explosion, and a considerable portion 
of the water is consequently drawn up in the wake of the 
original column overlying the charge. 

As already stated, we are still far from being able to give Approximate rule 
any fixed rule by which the sizes of charges may be calcu- turn of sizes of 
lated ; but as it is better to be above than below the mark, 
we may assume, till a definite rule is established, that no 
charge should be less than 500 pounds of powder, which 
should be used in all cases up to a depth of 20 feet. As a 
limit in the other direction, we may assume 2,000 pounds 
of powder as a maximum charge to be adopted, to be used 
at a depth of not less than 40 feet of water. This latter 
size is not too large to handle with comparative ease. In 
considering the series of charges given by Captain Harding- 
Steward, as the result of the confederate experiments, we 
find that the square of the depth in feet gives very nearly 
the sizes of the charges of powder in pounds for depths 
between 20 and 40 feet, for mines laid on hard bottom, and 



charges. 



46 

if we add one-fourth to the sizes of charges thus obtained, 
for soft muddy bottoms or buoyant mines held by moor- 
ings, we shall have a tolerably accurate means of approx- 
imately calculating the charges required between depths of 
20 and 40 feet. This relatiou .of charges, as the squares of 
the depth, though not derived from any mathematical re- 
lationship between the forces existing, is a rule easily 
remembered, and which seems to give a result sufficiently 
near the mark for practical purposes. Charges of the sizes 
above mentioned would seem to be sufficient to sink any 
vessel passing fairly over them. The ships would draw 
more water in proportion to their size and strength, and, 
bearing in mind the rule that where practicable the mines 
should always be laid on the bottom, they would find in- 
creased charges opposed to them in proportion to their draugh t 
of water. 

The force required to break through the bottom of a 
vessel, so strongly built as a modern man-of-war, has yet 
to be determined, and may lead to considerable modifica- 
tions in the strength of charges here suggested, 
proportion, as In the event of any other explosive than gunpowder 

compared with *. . . 

gunpowder, of being used lor submarine mines, as, tor example, it it is 

() t ll £ r ©xDlosivGs 

to'be nsed iii caicu- found that gun-cotton, fired with a detonating fuse, pro- 
duces better results, it will only be necessary to discover 
the relative proportionate value due to the force generated 
thereby, as compared with gunpowder, and apply it to the 
approximate rules given, in order to obtain similar informa- 
tion for the particular form of explosive used. There are 
again many places where gunpowder only may be obtain- 
able and its use becomes a necessity, there being no choice 
in the matter. 
interval between The next point to be considered is the interval to be 
allowed between two adjacent charges in the same line of 
submarine mines, so that the explosion of one shall not 
injure those next to it, or disturb the arrangement of their 
electrical cables, and yet that the chance of a vessel, run- 
ning between any two, and thus escaping injury, may be 
reduced to a minimum. 

This is a point on which nothing has yet been definitely 
determined, but is of so much importance that a series of 
experiments should be made as soon as possible, with a 
view thereto. 

The interval between any two mines, which would place 
one at such a distance from the other as to secure safety in 
the event of either being exploded, manifestly depends upon 
the size of the charges employed, or, in other words, the 



47 

distance at which any given charge is calculated to act 
destructively. This may be approximately calculated, 
when gunpowder is used, from the equation 



R = v 7 8 c, 

(see page 33,) where R is the radius of destructive effect. 
If then we place our mines in line at central intervals of 
six times R, our present experience goes to show that they 
will be safe from the explosion of those adjacent to them. 
To find the safe interval for gnn-cotton, or any other ex- 
plosive used in a system of mines, it will only be necessary 
to multiply by the co-efficient, derived from actual compari- 
son of the effect with that of gunpowder, to determine the 
value of R due thereto, and to arrange the mines in line 
at intervals of 6 R as before. This necessary interval be- 
tween the charges in line is one reason which renders the 
employment of two or more lines of mines essential to a 
proper maintenance of the defense. It also sufficiently ex- 
plains the objects to be attained, in placing them in such 
a way that the charges in the second line shall cover the 
intervals in the first, and that those in the third shall cover 
the intervals in the second, and so on. 

Again, with regard to the distance to be allowed between interval between 
any two lines of mines, it is easily seen, by reference to Fig. eac mmes " 

1, page 15, that just in proportion as we move our second 
and third lines back, we increase the chance for a vessel to 
pass safely through ; it is, therefore, desirable to keep these 
lines as close together as the other conditions of the case 
will admit. These other conditions are, first, the necessity 
for allowing a sufficient distance between the lines of mines, 
to enable the electric cables to be laid in a safe position 
midway between them, in carrying them to the electrical 
room from which the system is to be worked. Second, the 
necessity for placing the lines at such intervals that there 
shall be no confusion in determining the position of each . 
mine, by intersection, after the}' have been submerged. 
This is absolutely necessary in case it is required to fire the 
mines by judgment, the position of a vessel being determined 
by intersection, or cross-bearings, as it is sometimes called. 
It is also necessary to facilitate the discovery of a mine, in Experiments re- 
case it is required at any time to take it up for inspection Ee^stwic^cf 
And third, the average length of a large ship of war is an safety • 
item which must be taken into consideration in determining 
the distance above required. Keeping these conditions in 
view, the intervals between the lines may be approximately 
determined and, as a general rule, they should never be at 



48 

less than 100 yards or more than 200 yards apart, unless 
such an arrangement is incompatible with the peculiar cir- 
cumstances of any particular position to be defended. 

It would be very desirable to make a few experiments, 
with, a view to the more definite determination of this ques- 
tion of distance, at which one charge would be safe from the 
effect of the explosion on another ; till this is done the above 
general rules may be adopted. 
Experience of In the record of the destruction of wrecks in the river 

Lieutenant Wal- 
lace, r. e., as to Hooffly, by Lieutenant Wallace, R. E., he mentions that one 

distance of safety. & J ' J ' ' 

of two charges of 450 pounds each, placed 55 feet apart and 
at a depth of 48 feet of water, was destroyed by the explo- 
sion of the other, probably stove in ; it is not said how dam- 
aged. This distance of 55 feet is manifestly far too little 
for safety with a charge of that size ; it is, however, men- 
tioned here as the only experiment which I have been able 
to find which in any way touches on this point. 



CHAPTER IV. 

FORM AND CONSTRUCTION OF CASE. 

The next point to be considered is the form and construc- 
tion of the case to contain the charge of powder, or other 
explosive. 

Let ns first enumerate the several conditions which it is 
necessary that this case should fulfill. 

1st. It must be very water-tight to prevent damage to fu gjf e d d itions t0 bo 
the charge by leakage. 

2d. It must be sufficiently strong to bear handling, with- 
out danger of becoming leaky by straining, and must be 
able to sustain the external pressure duo to the depth of 
water at which it is to be placed. 

3d. When gunpowder, or gun-cotton fired with an ordi- 
nary fuse, is used, it must be sufficiently strong to hold 
the charge together, as it were, for an instant at the 
moment of ignition, so that its full effect may be obtained 
by as thorough a combustion as possible of the charge. 
When gun-cotton, fired with a detonating fuse, is used, our 
present experience seems to indicate that the case need only 
fulfill the conditions, as regards strength, enumerated in 
paragraphs 1 and 2. 

4th. In the case of a buoyant mine, it must be capable of 
being arranged with a large excess of flotation, so that 
when moored it may remain as stationary as possible at the 
required point. 

5th. It should be of such form as to be capable of being 
handled and moored conveniently. 

6th. It should be of such a form as to secure a thorough 
ignition of the charge with the smallest possible number of 
fuses. 

7th. It should be of such form as to be easy of construction 
and not too costly. 

First, with reference to the form of case. Those hitherto General form of 

7 case. 

used seem to have been either conical (see Fig. 4) or cylin- 
drical. The former appear to have been used by the con- 
federates as the general shape for their self-acting mechanical 
torpedoes. The apex (a) of the cone forms a convenient point 
to which the mooring-cable may be attached, while the base, 
terminated by a curved portion, (&,) serves as an air-chamber, conical form for 
giving the necessary buoyancy to keep the mooring-cable taut, SLtS^mlSo?* 1 
4 



50 



and hold the mine in a com- 
paratively stationary position 
in a current or tide-way. This 
see 01 s a very good form for 
self-acting mechanical mines, 
giving a good salient position 
on which to place the bosses 
to be struck by a passing ves- 
sel, as at c, c, c, 
cylindrical form The cylindrical form appears 
charges fired by to have been used by the con- 

clpctricitv 

federates, where they allowed 
their charges to rest on the 
bottom. The cylindrical shape 
admits of the charge being 
stowed in a very convenient 
form, and, for large charges, 
possesses advantages, as far as 
the ignition is concerned, as 
will be -hereafter described. 

The Austrians have adopted a cylindrical shape for their 
buoyant charges, and those exhibited by them at Paris were 
of the forms shown in Figs. 5 and 6. These mines were 





Fig. 5. 




arranged to be fired by electricity, and, all things considered, 
the cylindrical form seems the best adapted for the size of 
charges recommended by them, viz, 370 pounds of powder, 



51 

whether arranged to be laid on the ground or to be floated 
from moorings at any required depth. 

It is impossible at present to lay down any definite rule 
as to the form of case best suited for submarine mines ; be- 
fore this is done some experiments must be made with large 
charges of powder. All that has hitherto been done seems 
to point to the cylindrical as the best practical form, except 
for the case already mentioned, where comparatively small 
charges, to be fired by mechanical self-acting means, are to 
be used. 'A spherical form would be theoretically the best, 
supposing a single point of ignition only to be used, because 
every part of the outside would be equidistant from that 
center of ignition ; but the construction of a case of this 
shape would be comparatively costty, and a cylinder, the 
height of which approaches nearly to its diameter, is suffi- 
cientl}' near in shape to a sphere for practical purposes. 

Xext, as regards the material of which the cases may be 
most advantageously constructed. 

Several substances have been suggested and tried for Materials of 
this purpose, such as wood, iron, and vulcanized India rub- be composed. 
ber. The confederates appear to have used wooden barrels 
for their smaller charges, and cases of boiler-plate iron for 
their larger charges. 

The large charge of 1,750 pounds which destroyed the 
Commodore Jones in the James Eiver, and that of similar 
size which so narrowly missed the Commodore Barney, 
were both in cases of boiler-plate iron ; these charges were 
both fired by electricity. A charge of 5,000 pounds of pow- 
der in an iron boiler, arranged to be fired by electricity, was 
placed at a distance of 1,500 yards from Fort Sumter, at 
Charleston; at the critical moment, however, it failed to 
ignite from some unknown cause, which was probably 
either a defect in the insulation of the electric cable, or a 
bad^fuse. This charge had been four mouths under water 
before any attempt was made to fire it, and the art of test- 
ing fuses and insulation was not then known as it is now. 

The following is a description of the construction of the . 
cases for submarine mines, exhibited by the Austrian war 
department, at Paris, in 1867. 

The form and arrangement of the charge of a gun-cotton Forms of case 

t , • ,i -ij_i used by the Aus- 

inme in a wooden case is shown in the accompanying sketch, tr ians. 
Fig. 5, which gives an elevation and section. It consists of 
two strong wooden cases, one within the other; the inner 
one covered with zinc and the space between them filled in 
with tar. They are of the shape of a truncated cone, but the 
diameter of the bottom is very slightly greater than that of 



r >2 



the top. The inner one has a mean diameter of about 4 
feet, and is about 4 feet in height ; it is calculated to con- 
tain 4 hundredweight of gun-cotton, made up in coils and 
packed with plenty of air space, as shown in section, Fig v 5 ; 
in this section the air-space is shown dark. Abel's com- 
pressed gun-cotton affords great advantages over that in 
coils, as applied bj the Austrians. The size of a given 
charge of cotton is thereby reduced from three times that 
of powder to nearly an equal bulk, weight for w T eight. 
Figs. 6 shows an elevation and section of an iron case, cal- 



Fig, 6. 





culated to contain about 3 hundredweight of gunpowder. 
It consists of an outer cylinder, (a,) at the top of which is a 
series of projecting buffers, held in position by strong 
springs, by the contact of which the circuit from the firing 
battery through the fuse is completed by a vessel passing 
over the torpedo. These buffers are shown in the sketch 
at the points &, &, b. Within the inner case a second iron 
cylinder (c) is placed to contain the charge of powder, a 
sufficient air-space, to give the requisite buoyancy, being 
allowed by the difference in size of the cases. The outer 
case is about 4 feet in diameter and 4 feet in height. 
captain Harding Captain Harding Steward, E. E., has suggested placing 
t?oM a?to tKse the charge in an India-rubber bag, the bag being furnished 
bags. Indm ' rubber with an outer covering of iron. This outer covering need 
not be necessarily water-tight, and is only intended to 



53 

protect the India rubber from injury by friction against 
rocks, &c, and to give rigidity to the whole apparatus, 
so that it may be easily handled, and, when required, 
moored by means of anchors in the usual way. In some 
experiments tried by the confederates it was found that a 
large charge of powder inclosed in an India-rubber bag did 
not produce the same amount of explosive effect as the 
same charge in an iron or wooden case of considerable 
strength. It is probable that the envelope was burst by 
the first explosion and a portion of the charge wetted before 
the whole of the powder had been ignited, and in order to 
obviate this result, Captain Steward proposes to ignite the 
charges at a great many different points, so that the whole 
may be fired as it were simultaneously, and the drowning 
effect thus partially obviated. This is done by a. single 
fuse placed at the extremity of a metal tube, passing through 
the charge, and the tube being perforated at intervals, the 
flame and gas of a small priming charge is driven into the 
body of the main charge at a large number of points simul- 
taneously. A more minute description of this arrangement 
will be given in treating of the several modes of ignition 
applicable. It is to be remarked that the confederates only 
used one fuse in their charges, whatever their size might be, 
and this is quite sufficient to account for the non-ignition of 
the whole of the powder in a large charge when inclosed in 
an India-rubber bag only. The advantages of Captain Stew- 
ard's system are the comparative cheapness of the case, and 
that it is not dependent on the iron outer covering for keep- 
ing the charge dry ; this covering may consequently be 
made by a comparatively inferior workman. 
In removing the wreck of the steamer Foyle, sunk in the india-rubber 

bags used in con- 

Thames at Barking Keach, which service was performed by nection with oper- 

the officers and men under instruction in the School of Sub- Foyie. 

marine Mining, Chatham, the charges were all inclosed in 

vulcanized India-rubber bags, within an outer casing of 

half-inch boiler-plate iron. It was intended that the outer 

iron coverings should have been water-tight, but by some 

accident one of these cases leaked considerably ; the charge 

was, however, saved by the India-rubber bag, and performed 

its work apparently as w r ell as any of the others. This leak 

was attributed to the fact that the iron case had been left, 

for some time before it was filled with powder, in a hot sun; 

in fact, the air inside felt very hot to the hand. When 

subsequently submerged, it was supposed that the cooling 

and consequent contraction of the air had caused a consider 

able increase of external pressure, and that the water had 



51 

forced its way through some weak place. All the iron cases 
used had been tested by hydraulic pressure, and were 
apparently sound before immersion, yet the fact of the water 
having got into the case is indisputable. One lesson learned 
from this occurrence is, the advantage of using two water- 
tight cases for submarine mines, an inner one to hold the 
charge, and an outer one to withstand the pressure of the 
w r ater and to secure the necessary amount of flotation, 
Mines should not when the mine is required to be buoyant. Assuming that 
in the sun°dr a?a the leak was occasioned by the cause above specified, it is 
ugi empeiame. Decessar y ^ keep iron cases out of the sun, and fill them 
with the air inside at a temperature somewhat similar to 
that of the water in which they are to be placed; and 
again, when it is necessary to store them, especially in po- 
sitions, where they may be subjected to considerable changes 
of temperature, the screw-plug or man-hole should be left 
open to allow a free ingress and egress of air. As a matter 
of precaution, this should be made a general rule whenever 
it becomes necessary to store these cases ; this course is 
adopted with regard to large iron buoys. 
Report of Lieu- The following report by Lieutenant Ohadwick, E. E., on 
r. e., on boiler- the subject of boiler-plate iron, as applicable for use in the 

plate iron for sub- . ' . . „ , . . . , i , 

marine mine cases, construction of submarine mines, possesses considerable m- 

Fig. 7. 




/o. o 




Liir 



£.'■£• 




/O ■ O 

terest. Theresults of Lieutenant Chadwick's investigations 
are, that envelopes for submarine mines should be double, 
an exterior wrought iron case, and an internal tin or India- 
rubber case, to contain the powder, leaving an air space of 
1J inches to 2 inches between the two, and kept apart by 
wooden battens. The general form of case is shown in Fig. 
7. This air-space is to prevent the interior case, con- 



55 ' 

taming the powder, being damaged by any slight leakage, 
or by the deposition of moisture produced by change of 
temperature. In buoyant mines a considerable air-space is 
required to gixe the necessary flotation. 

For a buoyant mine it is recommended that the case 
should be of B B boiler-plate iron throughout, the sides 
J inch, and the ends f inch thick, fixed together by rivets, 
bolts, and nuts of the same material and quality. The 
size for a buoyant mine U i contain a charge of 1,000 pounds, 

might be 10 feet long and 2 feet 9 inches in diameter. This 
gives an amount of buoyancy as determined by the follow- 
ing calculations : 

1. To find the displacement : Displacement. 
Volume = length x area of base, (taking no account of the 

carved ends.) 

= 10/ X 1W^-A X * 

16 x 4 
= 10' x 5'.939 
= 59'.39 cubic feet. 
Displacement = volume in feet x weight of 1 cubic foot 
of wa^er. 

= 59'.39 x 62.425 pounds = 3707.42 pounds in fresh water • 
or 59.39 x 64.05 = 3793.93 in salt water. 

2. To find the weight of the mine : 
Area of skin = length x circumference. 

= 10'x i^X 3.1416 
4 

= 10' x 8.639 

= 86.39 square feet. 

Now I" plate weighs 10 pound per square foot, (Eankine;) 

therefore weight of skin = 86.39 x 10 pounds = 863.9 

pounds. 

Weight of three joints each 3" wide : 

= 3 x circumference in feet x width x 10 

= 3 x S'.64 x i' X 10 

= 64.8 pounds. 

Weight of 4 joints, (longitudinal,) = 4 x 2J xj X 10 

=: 22.5 pounds. 

Weight of 2 circles of angle-iron, 3' in diameter at 4.2 

pounds per foot, running: 

= 2 x % X 3.1416 x 4.2 
4 

= 59.38 pounds. 

Each end is a segment of a hollow sphere, the diameter 

of the base being 2 feet 9 inches, and the height 6 inches. 

The thickness of metal is f inch. 



Weight. 



Flotation. 



Collapsing pres- 
sure. 



56 
Using the formula for the surface of a segment of a sphere : 

S = TV . d . h 

IV 
we find the surface of the two ends = 2 x 3.1416 x -j- X \' 

= 8.64 
weight = 8.64 x 15 pounds 
= 129.6 pounds. 

Summary of Weights. 

Pounds. 

Skin . : 863. 90 

3 joints ... 64. 80 

4 joints, (longitudinal) 22. 50 

2 rings, (angle-iron) 59. 38 

2 ends, (domed) 129. 60 

Charge 1, 000. 00 

Case for do 150. 00 

Total weight 2. 290. 18 

3d. To find the flotation : 

Fesh water. Salt water. 

Displacement 3, 707. 42 3, 793. 93 

Weight 2, 290. 18 2, 290. 18 

Flotation 1, 417. 24 lbs. 1, 503. 75 lbs. 

This may appear unnecessarily large, but it is well to 
have an excess of flotation power, as it can easily be dimin- 
ished by using a slightly larger charge.* 

The dimensions given above are sufficient to resist any 
tendency to collapse from external pressure. 
Let I = length in inches. 
d = diameter. 
t = thickness. 
q — collapsing pressure per square inch. 

Then q = 9672000 ^— nearly,- (see Bankings Applied Me- 

chanics, page 307.) 

i 
Therefore, in the present case, q = 9672000 M 

±Z\) X oo 

= 152.6 lbs. per square inch, 
which represents a pressure of about 350 feet depth of water. 
This calculation is uijtde without regard to the covering plates 

over the joints, whicK would probably quadruple the strength, 

— / 

* The amount of flotation necessary depen ds on the strength of the 
current in which a buoyant submarine mine is moored, as will be ex- 
plained hereafter. 






57 

as three such joints would exist, the case being conveniently 
formed of four plates, and consequently /, the length for 
calculation, would become 30 instead of 120. 

The strength to resist internal bursting pressure is given 
by the equation 

-=^ (Eankine.) 
r / 

Where t = thickness. 

r = radius. 

p = bursting pressure. su ^ rsting pre " 

/ = tenacity, which may here be taken as 

34,000 pounds per square iuch. (Eankine.) 

Then ^ — ^ 
inen lo\5 " 34000 

or, p = 515 pounds per square inch. 

Therefore bursting pressure is nearly 520 pounds per 
square inch. To develop the whole force of the powder, 
when fired in the ordinary manner, a much greater strength 
would probably be necessary ; but to obtain it, the thickness 
of the case would have to be increased to so great an extent 
as to render it unmanageable. It would appear, therefore, 
that to produce a given effect it would be better to employ 
an excess of powder, ignited by several fuses, than to at- 
tempt to produce a maximum effect from the charge by 
increasing the thickness of the case. It might be well to 
try, on a considerable scale, the effect of inclosing the pow- 
der in a loosely-woven bag of gun-cotton, with the object of 
igniting the charge from the exterior, by which the disper- 
sion and loss of part of the charge might be prevented. 

There is no doubt that, under ordinary circumstances, we 
should use a cylindrical case, more approaching in form to 
that adopted by the Austrians, and shown in Figure 6, than 
to that given by Lieutenant Chadwick, shown in Figure 7; 
this latter was designed to be moored fore and aft, as would 
be necessary in a very strong current. Our present experi- 
ence goes to show that, in a three or four knot current, a 
single mooring-hawser will answer every purpose, pro- 
vided plenty of buoyancy is given to the miue. 

We have as yet no sealed pattern of an approved form of 
case for submarine mines, and till one is determined on, it 
is only possible to deal in general terms with the subject. 

A good many experiments have been tried by the float- Result of ex- 

-,. . . . . , . . periments on 

mg obstruction committeee, to ascertain the requisite strength of case, 
strength of case to fulfill the necessary conditions already straction eommit- 
enumerated, and the following appears to be the result of ee 
their investigations, so far as carried out : 



58 

"These experiments lead to the general conclusion that 
the effect of a charge of gunpowder exploded under water 
is enhanced in a very great degree by the strength of the 
case in which it is inclosed, seeing that even with so small 
a charge as 4 pounds the maximum effect of the force is not 
attained until a case is provided of ^-inch iron, and which 
will stand a gradual jnessure from within of 330 pounds 
per square inch. 

" It may therefore be assumed that the manageability of 
a charge will alone determine the maximum weight or 
strength to be given to a torpedo, and that all the strength 
which it. may be found necessary to give to the case, in 
order to resist the pressure of the column of water under 
which it is submerged, will tend to increase the effective- 
ness of the charge, there being no risk that such extra 
strength of case will involve an expenditure of force, in its 
rupture, at all approaching in extent to the advantage 
gained by its resistance, and the consequent increase of 
time afforded for the development of the explosive force of 
the charge." 

A corroboration of this opiuion appears in the account of 
the experiments on board the Excellent, where the effect of 
5J pounds of powder in a shell approximated to that of 
25 pounds in a barricoe. 
Experim ents It only now remains to continue the series of experiments 
^quii a Jif ec aiges with large charges, of such size as would be used on actual 
service, to enable a definite conclusion as to the form and 
strength of case best suited for the purpose, to be arrived 
at. The charges hitherto used in the experiments carried 
out have been small, as the apparatus would not admit of 
large charges being fired in connection with it. A continu- 
ation of this series of experiments, in connection with an 
apparatus of similar form, but on a larger scale, under the 
direction of the royal engineer committee, is now being 
carried on, from which more definite results will no doubt 
be obtained. These experiments are not, however, suffi- 
ciently advanced to warrant any decided conclusion upon 
the results obtained from them. 
cylindrical form As far as we yet know, I think we may say that a cylin- 
mendeT re ° om ' der of a more or less elongated form seems to fulfill the re- 
quired conditions best, but whether it should be of India 
rubber, protected as described, of boiler-plate iron, or of 
any other material, has still to be determined. Should, 
however, boiler-plate iron be decided on, I think we may 
safely assume that a thickness of J inch of metal (the burst- 
ing pressure for which, on an elongated case, of the dimen- 



59 



sions shown in Fig. 7, calculated to contain 1,000 pounds 
of powder, would be 515 pounds on the square inch) will 
give a sufficient resistance to the bursting effect of the ex- 
plosion for the size of charge recommended. 

Iu all cases, the most approved form of envelope to con- 
tain a charge of powder for submarine mining purposes, shift. 
may not always be at hand, and it may be necessary to 
use ordinary barrels, or any other available articles. Bar- 
rels are very readily obtained anywhere, and, when properly 
strengthened, are a tolerable substitute for the more ap- 
proved form of case; they are, moreover, made of sufficient 
size to contain a considerable charge of powder. 

In blowing up wrecks in the river Hoogly, as reported 
by Lieutenant Wallace, E. E., in Volume XYI of the Pro- 
fessional Papers of the Eoyal Engineers, page 116, barrels 
were used. These were of different sizes, viz, hogsheads, 
half-barrels, and kilderkins, holding respectively 500, 300, 
and 150 pounds of powder. Lieutenant Wallace tried sev- 
eral methods for strengthening the two larger sizes, which 
he found necessary, and that employed by Sir Charles Pas- 
ley, in his operations upon the wreck of the Eoyal 

George, and shown in the annexed 
Fig. 8, was found to be the 
most effectual. It consists in 
strengthening the ends of the 
barrels with wood. The project- 
ing tops of the staves of the orig- 
inal barrel were half cut away? 
and the strengthening of wood 
arranged to break joint with 
them, while at the same time fill- 
ing up the spaces cut away. 
This done, the whole barrel was 
well payed over with pitch and 
tar, and, when required to re- 
main a considerable time under 
water, the whole was sewn up in 
a stout canvas covering, also well 
saturated with the same composi- 
tion of pitch and tar. Lieuten- 
ant Wallace found that, in a 
strong tide-way, a charge of 500 
pounds of powder required a 
weight of 400 pounds to sink it, 
whereas in slack water, less than 
half that weight was sufficient. 



Barrels may be 
led as a make- 



Fig. 8. 





60 

ah cases must As in submarine mines the charges must generally remain 
tight™ 7 r a considerable time under water before explosion, it is most 
necessary to make the case, whatever it may be, very water- 
tight, and with this view the inside of a barrel might be lined 
with a coating of marine glue or cement. In the experiments 
carried on by the floating obstruction committee, the latter 
was found to give a perceptible increase of explosive effect, 
when used as an external coating to X X tin cases for small 
An internal tin charges, by giving an increase of time for ignition. An inter- 
be'r bag recom- nal case of X X tiu would also, I imagine, prove a very effect- 
tne n charge dry! !ep ive means of keeping the charge dry. In using it care should 
be taken to fix it firmly inside the barrel, as any independent 
motion might disturb the connections of the electrical con- 
ducting wire or destroy its insulation. An internal India-rub- 
ber bag, as recommended by Captain Harding Steward, 
placed inside a barrel would also afford a ready means of 
preserving the charge in a dry state. 

If greater flotation than that afforded by the barrel, when 
loaded, is required, in order to fit it for a buoyant mine, it 
must be given by buoys or corks attached to it. 
a steam-boiler Another make-shift which may be used for submarine min- 
3 shlft ' ing purposes is a steam boiler, aud any other envelope 
presenting the necessary requisites of strength, to resist the 
external and bursting pressure at the moment of ignition, in 
a sufficient degree to insure a good explosive effect, and 
also possessing the property of being very water-tight, would 
answer the purpose. In all cases it would be necessary to 
use the same precautions in the preparations of these arti- 
cles as recommended for the barrels, and which indeed are 
the essential points to be attained in any envelope for sub- 
marine mining purposes, whether of a make-shift character 
or constructed especially for the purpose. 
a strong case These remarks, with reference to the strength of case 

essent ial with , , , ,. ,. jC£ , , „ . , 

gunpowder o r necessary to develop the explosive effect of any given charge, 

witn CO an° ordinal have reference especially to gunpowder; and as circum- 

cotton^rSed with stances may occur in which gunpowder alone is obtainable, 

ft ifnors^lssen! they must not be omitted in consideriug the organization of 

tial - any system of submarine mines. If any other explosive be 

used, the necessity for employing a case of sufficient strength, 

with reference to the peculiarities of that explosive, must 

still be kept in view. Compressed gun-cotton fired with an 

ordinary or with a detonating fuse is the most likely agent 

to be employed. If fired with the ordinary fuse it would 

still be necessary to take the strength of case, to develop 

the full explosive effect of the charge, into consideration, 

and the conditions would be very similar to those of gun- 



61 

powder, bearing in mind that, where an equivalent only is 
used, a case of proportionately smaller size will be sufficient. 
If fired with a detonating fuse, we may probably omit the 
consideration of the strength of the case as far as the 
development of the explosive effect of the charge is concerned. 
The other conditions to be fulfilled, viz, capacity to keep out 
water, sufficient strength to bear handling without danger 
of fracture, &c, enumerated in the beginning of this chap- 
ter, must, however, be kept in view. 

It is impossible as yet absolutely to say that gun-cotton, 
fired with a detonating fuse, is our best explosive for sub- 
marine mines 5 but it possesses many advantages, not the 
least of which is this ability to dispense with all considera- 
tion of the strength of case necessary to the development of 
the maximum explosive effect. 



CHAPTER V. 

MOORING-. 

The next point to be considered is the mode of mooring a 
submarine mine when it is to be floated up from the bottom 
and not actually laid on it. 

The question of mooriug seems at first sight a very sim- 
ple matter; practically, however, it has been found to be 
one of the most difficult problems to be solved in connection 
with a system of submarine mines. In order to possess a 
maximum of efficiency, no indication of the position of a 
mine should appear on the surface of the water,* and yet 
the spot to within a few feet where it is deposited must be 
known to the defenders of the position in which it is used. 
It has been found that the least current, or even a moderate 
breeze, renders the placing of even a single mine in a defi- 
nite position a matter of very considerable difficulty. When 
a series of mines are to be moored in proper relative posi- 
tion, this difficulty is much increased, and it is again con- 
siderably augmented in proportion to the depth of water. 
Under certain conditions, therefore, special means, to be 
hereafter described, must be employed. 
objects to be at- The objects to be attained in mooring are as follows : 

1st. That the charge should be kept as nearly as possible 
stationary at the point where it is required to act. This is 
particularly necessary where there is a tide which, flowing 
first in one direction and then in another, tends to cause the 
mine to shift its position, and is indispensable in the case 
of mines to be fired by judgment. 

2d. The mooring should be so arranged that there shall 
be as little twisting as possible, which might break or injure 
the insulation of the electrical cable. 

3d. The anchors or heavy weights used should be suited 
to the nature of the holding ground or bottom. 

4th. Mooring-cables should be so arranged that they may 
not be likely to become twisted together or entangled. 

Buoyant submarine mines may be moored by one or more 
cables, according to the different circumstances of the case, 

* In certain cases it is impossible totally to couceal the position of a 
system of mines, as, for example, when there is a considerable rise and 
fall of the tide. When such is the case the very smallest indication pos- 
sible should be allowed to appear on the surface of the water. 



ained 



bo 



and several modes of mooring have been suggested and 
adopted. 

The following is a description of that used by the Ans- /ustri 
trians during the war in 1866, and exhibited by them at 
Paris in 1867 : 

In the Adriatic, where there is almost no tide or current 
to disturb submarine mines or cause them to revolve and 
twist up their mooring-chains, a very simple arrangement 
for keeping them in their required positions has been found 
effectual. This is shown in sketch Fig. 9, which gives the 



ian modi 
of mooring. 




Fig, 10. 



form employed with the original gun-cotton charges which 
were arranged to be fired at will. It consists of a simple 
wooden platform of triangular form, on which heavy weights, 
marked (k) in sketch, are placed at intervals; 
this platform is attached to the submarine 
mine by three wire ropes, in connection with 
its angles, which are fastened to three chains 
holding the charge at any depth below the 
surface of the water required, by means of 
arrangement shown in sketch Fig. 10. This 
consists of a pulley (?) attached to the ex- 
tremity of the wire-rope of platform, through 
which the mooring-chain of the charge is 
passed and fastened by a key or catch marked (m) at the 
required length by means of a self-acting arrangement 
shown in Fig. 11. This key is of considerable weight, and 
consequently slips down as the charge is hauled into its 
place, but the moment the chain is slackened the two arms 
(a, a) shown in dots which are made to allow the latter to 
pass through in one direction only, catch into a link of the 
chain and hold the charge firmly into its place. The ap- 




Austrian catcl: 



64 



paratus is so constructed as to allow the chain to be passed 
freely through it, aud is provided with nuts to admit of its 



_^.*— > 



Fig. 11. 





Austrian mush 
room anchor. 



Block and pul 
ley. 



being separated, in order to disconnect it from the chain 
when required. In our mooring experiments an apparatus 
of this nature, weighing 60J pounds, has been used in con- 
nection with a half-inch chain with good results. 

In connection with the self-acting submarine mines more 
recently adopted, a mushroom anchor has been used. This 
mode of mooring is said to have been quite effectual in the 
still water of the harbors of the Adriatic. 

The details of the block and pulley used in connection 
with this key are shown in Fig. 12. The sheave (a) is made 
of cast iron galvanized, and the remainder of wrought iron. 
The sheave (a) and axle (6) were, in the first instance, made 
of gun-metal, but the electric action, set up between this 
and the iron of which the remainder was constructed, had 
the effect of decomposing the latter very rapidly, and the 
apparatus in consequence soon became useless. Experience 
teaches us that no two metals between which electrical 

should be placed in contact in sea- 
quite sufficient to induce voltaic 
action, to the detriment of one of the component parts, and 
destroy the apparatus. An ordinary shackle is attached 
to the block to enable it to be fastened into a link of a 



Metals between action IS likely to OCCUr 

which electrical ., 

action occurs not water, as the latter is 

to be placed in 
contact in sea- 
water. 



65 



chain or thimble when required; when convenient it may 
be fastened directly into the eye of the mushroom anchor, 

Fig. 12. 





which, under certain conditions, would simplify the arrange- 
ments very much. The dimensions shown are adapted for 
a ^-inch chain. When new it works very well, but rust 
soon renders it stiff. 

Fi&'. 13 shows another description of catch by which a „ -. „ 

& sr j Barbed catch. 

Fig. 13. 





I'W 



charge, which has been hauled clown, may be held in its 
place. It consists of a simple pair of barbs, (b b,) working 
on an axle and held open by an India-rubber spring, (a a,) 
capable of being compressed; if pushed away from the 
India rubber they simply press against each other, shoul- 
ders being provided on each, close to the axle, to sustain 
any pressure exerted against them. To use this apparatus 
it is only necessary, after measuring the depth of water at 
the point where the mine is to be submerged, to insert the 
catch at the required distance in the mooring-cable below 
the charge, and haul down through a thimble or eye on the 
mushroom anchor or moorings, when the mine will be re- 
tained at the required depth below the surface. 

It possesses the advantage over the Austrian arrangement, 
Fig. 11, that it can be used in connection with a hemp or 
wire cable, whereas the Austrian can only be used with a 
chain. 

.5 



66 

Catches of this kind have been used in our mooring prac- 
tice with very good results when new. When they have 
been sometime submerged the rust makes the joints very 
stiff. And they then become hard to pull through the ring 
or thimble in connection with them. The Austrain catch 
possesses the same defect, becoming very stiff from rust; in 
fact, any iron apparatus must necessarily be injured in this 
way, and, for the reasons already specified gun metal is in- 
admissible in close proximity to iron. The rusting is not 
perhaps of any very great importance, as, when once down 
into position, a mine would seldom be required to be moved. 
A series of experiments in mooring were carried on at 
Chatham during the autumn of 1867, and the following ex- 
tracts from the reports of Lieutenant O. Chadwick, E. E., 
who had immediate charge of these experiments, throw 
some light on the difficulties to be encountered in sub- 
merging charges. 
Experiments in « When the depth of water is so great that a submarine 

mooring m Med- x ° 

way. near Upnor mine, if placed on the bottom, would require for efficiency 
an excessively large charge, it must be floated up from the 
mooring to which it is attached. This introduces great com- 
plication in the arrangements and also increased chance of 
derangement, either by accident or by the operations of the 
enemy. For still, tideless waters, the Austrian method 
would no doubt answer. In any current, however, the case 
would be liable to spin round and entangle the conducting 
wire with the moorings and produce kinks in these, unless 
indeed the size of the triangle were inconveniently large. 
It is also easily grappled and taken up ; indeed one placed 
in the Medway at Upnor was, after a few hours, hooked by 
an anchor of a barge or steamer and carried away." 
Faulty arrange- While on the subject of methods of mooring when there is 

ment or mooring ° *-" 

caries. an y current, the following must be avoided : Fig. 14 shows an 

ordinary cask with two mooring cables (a a) underneath. 
The object of using two cables is to keep the mine in a per- 
fectly stationary x)ositi on, but our experience, derived from 
experiments carried on in the Medway, is, that unless the 
attachments of these cables to that mine are kept well apart 
they are certain to become twisted round each other when 
there is a current, and especially in a tide- way where it runs 
first in one direction and then in another. It is clear, too, 
that if, in the process of lowering or by any other chance, 
the mooring cables get a single turn around each other, 
the effect of their having been originally arranged apart 
is completely lost, and they become as free to revolve as if 
both cables have been attached to the same point. Practi- 



67 

eally it was found that with a current of about three knots 
an hoar, as in the Meclway, barrels arranged as in Fig. 14 

Fig. 14. 




invariably became twisted up in such a way that an electric 
conducting wire, connected with the mines to which they 
were attached, would inevitably have been much kinked 
and probably injured. 
To obviate such a result Lieutenant Chadwick proposes, small charge 

r ^ 7 moored on a spar. 

with small charges and at moderate depths of water, to lash 
the mine on a spar on which a rough frame- work to fit the 
form of the barrel had been arranged, and attach the moor- 
ing-cables to the extremities of that spar as shown in Fig. 
15, thus securing the necessary distance between the points 

*%. 15. 




of attachment to prevent the chance of entanglement. In 
order still further to secure this, the anchors to which the 
cables are attached should be placed well apart, and plenty of 



iuga. 



68 

Ladder moor- buoyancy allowed to keep the cables tight. In certain 
positions it may be inconvenient to place the anchors far 
apart, and when this is the case, a ladder arrangement may 
be effectively used. 



Fig. 16. Lanr mtsterLine 



Circuit C Lose 



M> 



n,,c 




Fig. 16 shows a combination of this sort, somewhat similar 
to that tried in connection with experiments on board Her 
Majesty's ship Cambridge. 

The following report by Mr. Charles Coekran, gunner, 
Koyal Navy, extracted from the report of the committee on 
active obstructions, published in 1868, gives the results ob- 
tained : 

a A buoyant torpedo, consisting of a 27-gallon iron oil- 
cask, containing 15 gallons of water, and a strongly buoyant 
nun-buoy to represent the circuit-closer, were fitted with two 
mooring-ropes from the circuit-closer to the torpedo and 
thence to the mooriug-ballast, the ropes being separated by 
wooden rounds or spreaders, one to three feet long, to resist 
the tendency to twist. This arrangement, with two insulated 
wires connecting it w r ith the electric battery, was placed in 
position on the 18th of April, 1868, in 10 fathoms water in 
a part of the Hamoaze liable to strong eddy tides ; and at 
the end of 24 days it was removed. While it was in position 
the arrangement was twice examined by divers, who reported 
the mooring-ropes and conducting-wires to be clear of turns j 



69 

and that, when taken up, a round turn was found in the 
mooring-ropes close to the ballast, but the whole of the upper 
portion of the ropes and the insulated wires were clear. 
This means of employing hemp-rope, in the absence of wire- 
rope, in a manner calculated to resist the revolving tendency 
of the circuit-closer, appears to have proved successful. 
It is, however, to be observed that the rounds or spreaders 
are liable to lodgments of sea-weeds or other, objects, which 
might sink the circuit-closer; and that the plan does not 
therefore recommend itself for adoption, except when wire- 
rope is not procurable. 

"The buoy-rope, which had been attached to the ballast 
for recovery after experiment, repeatedly took several 
turns around the mooring-ropes, though cleared by the 
divers at each examination." 

In Fig. 16 rather more spread is shown than was used in 
the Hamoaze experiment. This would no doubt decrease 
the tendency to twist, but the broader spreaders would af- 
ford a greater space for the deposit of sea-weed, &c. In 
deciding, therefore, on the particular dimensions to be em- 
ployed, local circumstances, such as the quantity of sea- 
weed or other floating matter, the strength and direction of 
currents, their steadiness or eddying qualities, and all simi- 
lar difficulties, should be carefully considered so as to insure, 
as far as practicable, a minimum of evil in the form adopted. 

In a tide-way where there is a current of more than five Mooring fore 
knots an hour, two anchors may be advantageously used, 
placed up and down stream at a considerable distance apart, 
depending on the force of the current and the height from the 
bottom at which the mine is to float. At first, considerable 
difficulty was experienced in placing the anchors at a correct 
distance apart, but by the following method small charges 
have been laid down successfully and have maintained their 
positions when so placed. 

The following arrangement, designed by Lieutenant Chad- 
wick, E. E., was tried in the river Meclway during the 
autumn of 1867, and moorings with a charge attached were 
thereby successfully lowered into position without much 
difficulty. 

A derrick, Fig. 17, was rigged at each end of a boat, the 
distance between the ends being that w r hich the moorings 
were to have when on the bottom. To these the mooring- 
anchors were suspended, being attached to the ropes by 
nippers which released them when on the bottom. The 
charge itself was made to sink by means of a heavy saddle, 
Fig. 18, placed over it, and thus its upward tendency did 



and aft. 



70 

not draw the moorings together; (a) shows the mine, (b) the 
weighted saddle. 




The length of the mooring-eables haviDg been previously 
adjusted according to the depth of water, when the moorings 
were placed on the bottom the saddle was drawn up, and 
the charge rose into its proper position. 




Fig. 18. 




Small charges, of the size of 18 to 36-gallon casks, were 
successfully placed in this manner with a 30-foot gig, ponton- 
baulks being used to form the derricks. 

The larger kind of ship's boats, such as a 42-foot launch, 
are provided with a windlass placed across the boat, in the 
center of its length. Under this are two hollow trunks fixed 
water-tight over holes in the bottom ; through these ropes 
may be passed to the windlass, and in this manner a heavy 
object may be carried under the bottom of the boat. A load 



e x- 
periment o: 

doc It- 
yard. 



71 

of from two to three tons may be safely carried in this man- 
ner. 

In order to place a large buoyant charge, of 1,000 pounds 
to 2,000 pounds, for example, three of these larger boats 
would be required to carry it and its anchors, one for each 
anchor or mooring-block, and one for the charge itself. 
They would be connected by a rope, which, if kept stretched, 
would insure the anchors being placed at the proper dis- 
tance apart. 

In some cases ponton-rafts, with triangle guys erected on 
them, might be used, but they would be difficult to manage 
in a current. 

Some further experiments were subsequently made in the Mooring 
Med way opposite Chatham dock-yard, where there was no Chatham 
chance of the apparatus being carried away by passing ves 
sels, as was supposed to have been the case with those 
placed in the river opposite Upnor Castle. The following 
is the result of these experiments as reported by Lieutenant 
O. Chad wick, R. E. : 

" Two large casks (36 gallon) were moored in the river Mooring by 

single cable. 

with mushroom anchors of 10 cwt. each. Their total buoy- 
ancy was about 10 cwt., and each contained a weight of 5 
cwt., representing the charge, so that there was an upward 
strain on the mooring-rope of 5 cwt. The length of the rope 
was 15 feet, so that the top of the barrel was about 20 feet 
from the bottom of the river. 

" The depth of water at low water was, in one case, 20 
feet and in the other 8 feet. 

" A clip-hook was first used to release the mooring from 
the tackle by which it was lowered ; but this was found not 
to answer, from the twisting of the rope when lowering, 
which caused the tripping line, in connection with the 
arrangement, to wind round the parts of the tackle. 

" The next plan used was a double rope, passing through 
a double block on the sheers erected on the raft and through 
the eye on the mushroom anchor. This arrangement also 
gave great trouble, from the twisting of the ropes together, 
and it was found impossible to clear the rope from the 
moorings w T hen a single mooring cable was used.'' 

Lieutenant Chadwick, in conclusion, recommends the fol- 
lowing mode of lowering mines into their places to be 
adopted : 

'■The mines, with their moorings attached, should be car- 
ried to the place where they are to be submerged, in a barge 
or lighter, provided with a derrick or crane, for taking them 
in and out. 



72 



ship's launch u Foy lowering them into position a ship's launch might be 

purpose?. m ° ng used, provided with the fittings shown in Pig. 19. In the 

center, or perhaps rather more forward, a crab-capstan, a, 

might be placed. Over the stern are two davits, (b b) with 




sheaves, their outer ends being about 6 feet apart. Between 
them is an inclined plane (c) on which the case (d) containing 
the charge is placed. 

" The mushroom anchor (e) is lowered by means of two 
ropes, attached to two eyes in its sides, as shown in Pig. 20. 

Fig. 20. 



e'-.a'. 




Each of these ropes leach through the sheaves in the end of 
a davit, and thence to the crab-capstan. By thus separating 
the ropes it is hoped that twisting may be avoided. 

" The mine should be placed on the inclined plane, and 
the mushroom anchor between the davits, by means of the 
crane in the shore lighter. This done, the boat is ready to 
be towed to the destined position of the mine. The anchor 
should then be lowered gradually down , and the mine launched 
over the stern. To detach the ropes by which an anchor 
has been lowered, common marline-spikes, well greased, and 
which are arranged to hold these ropes by being passed 
through a double heart-knot, may be used. These marline- 
spikes having been withdrawn by means of lines, (//) attached 
for the purpose, the anchor is thus released." 

A 32-foot pinnace is sufficient to lower an anchor or 
mooring-lump weighing 20 cwt. ; but for larger weights a 
larger boat would be required. 
Results of ex- a 32-foot pinnace having been fitted up as recommended 

periments in moor- , . 

ing with pinnace by Lieutenant Chadwick, a series of experiments were 
ant chadwlck's made with her during the summer of 18G8. The result of 
these experiments showed that, though this system an- 
swered remarkably well for lowering a mushroom anchor or 



73 

mooring-lump into position, and there was no listing or 
difficulty in detaching the ropes by which it was so lowered, 
there was still an immense amount of care required in 
handling the charge and circuit-closer in connection with 
it, in order to prevent damage to the electric cable and 
disarrangement of the lnooring-gear, and that even with a 
depth of only six or seven fathoms, at which the experiments 
were tried, and a three or four knot current, such as that 
of the Medway, it was so difficult to get a mine into any 
required definite position as to be practically impossible. 
The conclusion consequently arrived at has been that in 
most cases, and especially in deep water and with large 
charges, it will be necessary to lower the moorings first into 
the required position and haul the charges down to them, 
in order to insure that accuracy of position which is essen- 
tial when a mine is to be fired by judgment ; and in order 
to obviate, as far as possible, the great strain on the anchor, 
which necessarily occurs during the process of hauling 
down, the mine should be weighted, the weights being sub- 
sequently removed when the operation of submerging is 
complete. The bottom at the point where the apparatus .Soft muddy bot- 

• ^ L - torn very favora- 

was placed was soft mud, and consequently very favorable ble for mu ' 
to the mushroom form of anchor. The current runs about 

k 

three knots an hour at the point where the experiment was 
tried ; the top of one barrel was just awash, while the nioor- 
ing-cable of the other allowed several feet of slack, at dead 
low tide. The mooring-cable used was a 3-inch wire cable 
composed of a strand of Xo. 20 galvanized iron wires, and 
manufactured by Messrs. Xewall & Co. The result of this 
mode of mooring was most satisfactory • there was no twist- 
ing of the barrels and consequent torsion of the mooring- 
cable ; that barrel which was moved so as to be just awash 
at low water, seemed simply to turn a little, as indicated by 
a vane arranged to show above the water, but never to make 
even a single whole revolution, and almost immediately 
turned back again. The position of the barrel altered but 
little, whether the tide was running in or out, probably not 
more than two feet either way from a central point. There 
was, of coarse, more motion with the other barrel which 
had a considerable amount of slack cable at low water. The 
wire cable was a great improvement on the ordinary hemp 
cable, with which the barrels, }n the first experiments, were 
moored, and the mushroom anchor did its work remarkably 
well. 

The conclusions arrived at from these experiments seem conclusion 
to be as follows: that a single cable should be used when- from above 
ever possible, and that a wire rope is superior to a hemp nmen 



74 

one, being less likely to twist, kink, or wear from friction ; 
that a mushroom anchor is the best form for a soft muddy 
bottom. On a hard rocky bottom, the dead weight of the 
moorings must be depended on to keep a mine stationary, 
and, if a very heavy mushroom anchor is used, its edges 
should be furnished with toes or points, as shown in Fig. 
20, to catch in the crevices of the rocks. Plenty of 
buoyancy should be given to the case to keep the charge 
stationary ; buoyancy about equal to the weight of the 
charge will suffice in a current of four knots an hour, but it 
might be increased with advantage on a stronger current. 
With a current up to four knots an hour a single iron wire 
cable, with an anchor which holds sufficiently, will answer 
every purpose ; but where the current is very strong, with 
a rise and fall of tide, it will probably be necessary to moor 
with two cables, one from each end of the case, and two 
ordinary anchors. When two cables are used, they should 
be placed as far apart as possible, and the anchors well 
spread out, and the buoyancy should be sufficient to keep 
the cables very taut. From the experiments made at Chat- 
ham, it has been found that, two cables attached to a case 
close to each other, twist together immediately, and the 
case is by this means soon drawn down out of .position. 
When anchors are not obtainable, heavy blocks of stone 
or pigs of iron ballast, or any heavy weight, may be used 
to replace them for moorings. 

The following suggestion by Lieutenant Jekyll, E. E., 

is worthy of consideration, and would no doubt be found 

practicable in many cases, if not with very large, certainly 

with charges of moderate size : 

Mooring to a « Submarine mines used defensively will generally, if not 

heavy chain sug- . 

gested by Lieu- always, be rnoored in straight lines. 

E nan e y ' ' "In practice, the greatest difficulty is experienced in 
mooring any object in a particular spot, especially when two 
mooring- chains are required, as will sometimes be the case, 
to prevent twisting. I suggest that, instead of anchors, a 
heavy chain cable be employed to moor the mines. 

"A section of the channel to be defended having been 
made, the line assumed by a chain could be laid down to 
scale. The positions of the mines and their distances apart, 
depth from the surface, &c, having been arrived at by cal- 
culation, could also be laid down on the section. The 
points where the small mooring-chains of each mine meet 
the large chain would appear on the drawing, and the dis- 
tance of each point from either extremity having been 
measured off the scale, could be marked on the chain. 



75 

"Before sinking the heavy chain, the small mooriug- 
chaius should be rove through the links at the places marked, 
and the ends buoyed, sufficient length being allowed for 
the buoys to reach the surface. 

"The conductingwires could next be laid, and the ends 
attached to the same buoys which support the mooring- 
chains. In this way everything could be prepared, the 
cables tested, &c, before the mines were required at all ; in- 
deed, if the operation of fixing the same were practiced before- 
hand, it could be left out until there was considerable prob- 
ability of tbe mines being required for use. By keeping 
the mines ready loaded in suitable magazines, and having 
the Cables frequently tested, the probability of injury would 
be greatly diminished. 

"The great advantage of using a heavy chain would be 
the absolute certainty of having all the mines in their pro- 
per places j it would also simplify the moorings by doing 
away with a multiplicity of anchors and anchor-buoys. 

"A 2£-inch chain cable weighs 400 pounds per fathom. 
The mines would probably never be nearer than 70 or 80 
feet apart, so it is evident that the chain w T ould be quite 
heavy enough to counteract any flotation which would in 
practice be given to the mines." 

In a current of any strength, it would be necessary to 
use two parallel chains across the current, to prevent the 
mines swingiug with the change of tide, but the same ad- 
vantages would hold good. 

This idea is quite compatible with the system of hauling 
down the mines to previously placed moorings, as it would 
only be necessary to supply a pulley, of the form already 
described, shackled on to the chain cable at proper inter- 
vals, and with the necessary tackle rove through them. 

A modification, suggested by Lieutenant Bucknill, R. E., on Placing moor- 

¥- • .Tin, i t \ i • i < ii -««- i • ings in connection 

Lieutenant JekylFs plan, has been tried in the Med way, m 7 with a directing 
fathoms of water, and been found to answer very well. The byTYeuT?n e an t 
arrangement used was as follows : A strong heuipen cable was 
laid out across the river, from the mooring-lighter at Catness. 
the outer extremity being anchored. Previous to immersion, 
this cable was marked at intervals, at the points where it was 
intended subsequently to lay down the line of mines in con- 
nection with it. In this state it might have remained at the 
bottom of the river for a considerable time without injury, 
the slack having been taken up in order to keep it in 
a fair and even line, and prevent unnecessary movement. To 
place the moorings in position the following course was 
adopted : A mushroom anchor, with gear attached, having 



76 

been attached to one oi the davits of the pinnance, the direct- 
ing-hawser was slacked off sufficently to admit of its being 
underrun, and was passed over the bow 01 the boat at the 
fore row-locks 5 she was warped along to the position re- 
quired, as indicated by the mark previously made in the 
hawser. One end of a branch hawser was now bent on at 
this point, and the other extremity made fast to one of the 
eyes on the mushroom anchor, the necessary amount of 
slack being left to allow the anchor to be passed into its 
proper position. For small charges up to 100 pounds of 
powder, a distance of 30 feet, or a little more, from the 
directing-hawser would probably be sufficient, and, when 
no greater distance than this is required, it only remains to 
cut away the spun-yarn lashings securing the cable which 
retains the mooring at the extremity of the davit, and, thus 
set free, the anchor falls into its required place. On actual 
service, however, much larger charges than 100 pounds 
would be used, and it would be necessary to place the moor- 
ings at a greater distance than 30 feet from the directing- 
cable ; to do so, it is only necessary to veer out the branch 
cable, thus letting the boat drop down to the position re- 
quired, and cut away the lashings as before. The anchor 
having thus been got into position, any further arrangement 
for attaching the charge, electric cable, and circuit-closer, 
may be carried on without difficulty, 
favorable Favorable weather, and a proper direction of current, 

weather necessary . 

while placing especially m a tidal channel, are very essential to success 
moormgs m posi- w ^ en ^ p era ti 011 of getting moorings into position is 

undertaken, the difficulties being much increased by a fresh 
breeze and rough water. It must be borne in mind that, 
in order to insure a maximum of efficiency, the position of 
the moorings must be defined within very narrow limits. 



MaJtrv JSicuvser. 



Fig. 21 



O 



One or two lines of mines may -be laid on this principle 
in connection with a single heavy hawser or mooring-chain. 



77 

The general arrangement of a single line so constituted is 
shown in Fig. 21, and that of a double line in Fig. 22. 



o 



^-L— ,^____ _ | Main, j Eawser. 

Fig. 22. I 



i 



This plan affords considerable facilities for the examination Examination of 
of charges after they have been submerged. In order to charge™ 
reach any particular charge it would only be necessary to 
underrun the main hawser till the required branch was 
reached, by it to raise the mooring-anchor, and with it the 
mine to be examined. In the event of the main hawser 
being broken, it would not be a very difficult operation to 
grapple it and bring it to the surface for repair. When 
the main hawser is not in use for any of the purposes above 
mentioned, all slack should be taken in to prevent unneces- 
sary motion. This system appears to answer very well up 
to a depth of seven fathoms, and it would be very desirable 
to try it in very much deeper water. 

The fact that the exact position of a mine, within a yard, 
must be known to the defenders, must be always kept in 
view ; and in order to simplify identification as much as 
possible, an arrangement in lines, directed on some given 
point, will generally be best. This would seem to be an 
additional reason for placing the moorings first in correct 
position, and afterward hauling the mines down to them, 
and would seem to be the easiest and most practical course 
whether a single mooring cable is used or whether a mine 
is moored fore-and-aft to resist an extraordinary current, 
as, for instance, an unusual rise and fall of tide. In abroad 
channel and with deep water, as, for example, at Spithead, 
the difficulties of arrangement in lines would be increased, 
and probably in such a case it would be necessary to anchor 
a couple of large vessels fore-and-aft, and, after hauling them 



78 



tained. 



into the exact line, to connect them by a hawser, by which 
latter the boats engaged in lowering the moorings would 
be guided. 

It would, in many cases, be not only desirable but neces- 
sary to place the moorings in position at leisure in time of 
peace, and thus the most difficult and tedious part of the 
operation being done, a channel could, on a threatening of 
hostilities, be very rapidly put in a state of defense, 
rork- When an anchor has been placed in position it is neces- 
E-saryto retain the power of working the running-gear, in 
mfnt°must ai be n fe- co nliec tlon with the hauling-down arrangement, in a prac- 
tical form, and for this purpose the arrangement shown in 
Fig. 23 is suggested. In this arrangement a buoy (a) is 
placed in connection with one end of the cable, rove through 
the pulley (b) shackled on to the eye of the mushroom anchor, 
while at the other end an ordinary anchor (c) is attached. 
This latter is cast at such a distance from (a) that there is 
no chance of entanglement between the cable attached to 
the latter and that in connection with the anchor-buoy, (b.) 
By this arrangement it is manifest that, by weighing the 
anchor, (c,) both ends of the line rove through the pulley or 
loop (b) may be obtained at any moment with facility, and 
there is no chance of the two parts of the mooring-cable 
becoming twisted round each other, however long they may 
have remained submerged. It is essential to efficiency that 
there should be no such winding round each other of the 



Fig, 23. Water Xirw. 



£J 



d 



dy 



b 



two parts of the cable, as even a single turn would destroy 
the action of the running-gear through the pulley. If the 
buoy (d) cannot be conveniently used, the anchor (c) may 
be deposited in position without it, and, should it be 



79 

necessary to weigh it, the line (b c) could be easily grappled 
and brought to the surface, sufficient slack being allowed for 
this purpose. An ordinary weight of any sort, sufficiently 
heavy to counteract the upward pull of the buoy, («,) might 
be used instead of the anchor, (<?.) The buoy (a) should be 
kept some distance below the surface, as well to prevent 
injury to it by vessels striking it, as to keep its position, 
which would indicate that of a future submarine mine secret. 

A modification of this plan, shown in Fig. 24, has been Arrangement of 
suggested by Quartermaster- Sergeant J. Mathieson, R. Rested e ify dI Quaf- 
E. It consists in simply arranging two buoys, one at g^an? MathEson," 
each end of the running-gear, passing through the pulley RE ' 

l?ig. 24. Water Line. 



Qj 



or loop (c) in such a way that the buoyancy of one of them, 
as (&,) shall considerably exceed that of the other, (a,) and 
the latter, having been hauled down close to the moorings, 
would be held there till required to be moved. In such an 
arrangement care must be taken to make the buoy (a) 
sufficiently strong to resist the continuous pressure of the 
water at the depth at which it is required to remain. It 
possesses the advantage over the system first described of 
greater simplicity, but is more easily disarranged, for if the 
buoy (a) rose slightly, from any depression of the buoy (&,) 
there would be a certain amount of slack in the cable, and 
a consequent capability of entanglement by twisting around 
that part of it attached to (&,) which would at once destroy 
the efficiency of the combination. It has, however, been 
tried practically in the Med way, in five or six fathoms of 
water, with considerable success. 

Whichever of these plans is adopted, the utmost care is 
required in keeping the cables and buoy-lines clear during 
the process of lowering the moorings, as well as in subse- 



80 

quent manipulation, as any entanglement would be fatal to 
success, and more care is necessary with the second method 
than with the first. When laid down, too, they should be 
examined at intervals to see that the running gear is in 
working order. 
a mine on the Where a charge is to be laid on the bottom, it should be 

bottom must be , . . 

so heavy as to re- of sufficient weight to insure its remaining stationary, 
wnary. j^^^^ Wallace, in his account of the demolition of 
wrecks in the Hoogly, gives his experience as follows : 
" Sometimes, in a strong tide-way, a charge of 500 pounds 
of powder required a weight of about 400 pounds to sink it ; 
whereas in slack-water less than half that amount was suf- 
ficient." These weights, of course, refer to charges arranged 
in barrels, as used by him, and in all cases the weight of 
any particular form of case must be taken into account. 
Mode of placing The next point to be considered is the best mode of low- 

a charge in posi- . .... . 

«km. enng a heavy charge into Us position at the required depth 

below the surface, and, when lowered, of attaching it to the 
anchor. Two modes have been described by which this 
may be effected; either by first measuring the depth of 
water by sounding, then attaching the anchor, with the 
necessary amount of cable, and lowering both together, or 
by lowering the anchor first and drawing the charge down 
to it, and, when it has reached the required depth, there 
fastening it securely. 

The first plan is so simple that it requires no explanation. 
Our experiments have, however, proved that when it is re- 
quired to place a mine in position, th^ limits of which are 
defined, it is practically impossible of execution, except with 
small charges, very moderate depths of water, and favorable 
circumstances of weather and current. By the second 
method a mine may be placed much more accurately in 
position, and it is practically much more easy of execution. 
Barge used by The Austriaus employed a large boat or barge, on which 
mooring™ suw a derrick was erected, by which the anchor or mooring ar- 
rme mmes. raugement was first lowered into its place. To this anchor 

was attached a certain amount of wire cable, to the upper 
extremity of which was fixed a pulley, Fig. 10, already de- 
scribed. Before the anchor was lowered into the water, an 
iron chain attached to the case was passed through the 
pulley, and by it the charge was drawn down to any re- 
quired depth and there held by the self-acting arrangement 
previously alluded to, Fig. 11. 

When the heavily-weighted wooden platform, also used 
occasionally by the Austriaus for mooring purposes, was 
employed, the charge was held down to the required depth 



81 

by three mooring cables, one attached to each angle of the 
platform, and the only difference was that three pulleys and 
keying arrangements were required instead of one, as used 
with the anchor. The Austrians, however, carried on their 
operations where there was no tideway, but it is probable that 
a charge, moored by three cables in this way, might twist 
and be drawn .down if acted on by a current, unless the 
three points to which the cables were attached were placed 
very far apart. 

We have now had some experience in placing charges in 
position, by the method of hauling down to an anchor already 
laid, and keying by the Austrian and other catch described, 
and it is certainly not only quite practicable, but in many 
cases preferable to any other plan that we have tried. 

In our experiments at Chatham the apparatus at first Ponton raft 

... , -used for mooring 

used for placing the charges in position was composed of purposes. 
any materials that could be obtained on the spot ; and we 
have since gone into the question of the special apparatus 
and arrangements best suited for the purpose. Some of 
the charges moored in the earlier stage by a single mush- 
room anchor were lowered from a ponton-raft by means of 
a derrick erected thereon. A raft of this nature forms a 
tolerably good platform from which to carry on such an 
operation in smooth water. It possessed one serious disad- 
vantage, however, namely, that there being no gunwale, 
small stores were frequently pushed overboard and lpst. 
If, therefore, a ponton-raft is ever used as a make-shift for 
such a purpose, it would be desirable to add a temporary 
gunwale to it. Our experience in mooring submarine mines Experience de- 
niay be summed up as follows: When j)ossible, place the ments at chat- 
moorings in position at leisure, and be very careful to get 
them into the exact sites previously decided on for the 
mines. 

Arrange the running-gear in the simplest form, and try it 
at intervals to see that it keeps in good order. 

When a channel is to be put in a state of defense, bring 
the charges to the required point, and haul them down into 
position. 

With a current up to four knots an hour, a mine may be 
efficiently moored with a single wire-cable, provided plenty 
buoyancy is given. 

With a current of five knots an hour or more, charges, 
to be held in a defined position, should be moored fore and 
aft. For this purpose a double line of moorings is required, 
and in hauling down it is necessary to take care that the top 
is horizontal when the mine is in position. 
G 



82 

Mode of mooring There is one problem, with reference to submarine mines,, 
bie rise and fan of which has still to be solved, namely, that of mooring in a 
spot where there is a considerable rise and fall of tide, so 
as to show no indication, or at least a minimum of indication 
on the surface as the depth of water decreases. Many sug- 
gestions have been made with a view to the solution of this 
question, but none can be said to be completely successful. 

Mode ot moor- Quartermaster-Sergeant J. Mathieson, E. E., has suggested 

>.ng suggested by ° / oo 

Quartermaster- the use of a small bnov, just sufficient to give that amount 

sergeant J. Mathi- " 7 J & 

eson,RE. of flotation necessary to keep a circuit-closer always sus- 

pended at a given distance below it, the circuit-closer itself 
being slightly heavier than its bulk of water. The arrange- 
ments of this plan were found to be too delicate to be prac- 
tically useful ; the slightest leak in the small buoy at once 
disarranged the efficiency of the combination ; any lodg- 
ment of sea-weed or other floating matter was also equally 
fatal, as it increased the weight and consequently disarranged 
the very delicate balance necessary to successful working ; 
and the small buoyancy of the whole combination rendered 
it liable to be acted on by a comparatively small current 
and thrown out of position, which, for reasons already given r 
would be a serious objection. 
Mode of mooring Lieutenant W. E. Peck, E. E., has suggested the use of 

suggested by Lieu- ' ' OCT 

tenant w.E.Peck, a compressible buoy, arrange'd to act, through a pulley, so 
that as the water fell and the pressure was consequently 
reduced, it would expand, and, by the increased flotation 
thus acquired, draw a charge, in connection through a pulley 
Avith it, down. An India-rubber buoy might no doubt be 
made to fulfill the necessary conditions as to compressibility, 
but there would be great difficulty in getting any combina- 
tion so nicely balanced as that suggested must necessarily 
be, to work automatically through a pulley which had been 
submerged even for a comparatively short time; the friction 
occasioned by oxide has been found, under such circum- 
stances, to be very great. 
Mode oi mooring Lieutenant E. E. Moore, E. E., has suggested hauling a 

Lieutenant r. p. line of mines or circuit-closers down mechanically, by means 
of a cable connected therewith made fast at one extremity 
and passing through a fixed pulley to a windlass at the 
other. The lixed extremity of this regulating cable and the 
pulley, through which it passes to the windlass, must both 
be below the lowest level to which it is necessary to haul 
down the mines, and consequently below the surface of the 
water. In order to raise or lower the mines thus arranged 
it would only be necessary to slack out or haul in the cable. 
by means of the windlass as required, and it is easily seen 



83 

that a comparatively small amount of cable taken in or let 
ont would effect the necessary difference of level in the 
mines. In such a combination the mines should have plenty 
of buoyancy. 

In this system it is to be feared that the friction, insepar- 
able from the use of pulleys submerged for auy length of 
time, would act prejudicially. This combination has still to 
be tested ; it seems, however, worth trying, and if success- 
ful might probably be used in certain positions with advan- 
tage, especially if the number of mines attached to each 
cable is not very great. 

In the absence of anv reliable system of mooring, to ful- stationary ar- 

■.,, , . " . , . -, raugeinent o t' 

till the necessary requirements with a considerable rise and moorings for a 

' ., channel with con- 

tall ot the tide, and tor the present we cannot lay (town anysiderabie rise and 

, » . , ... -,'j -i-ni fall of tide. 

definite rules on this point, it would be necessary to arrange 
the mines to iioat at such permanent levels as to be suffi- 
ciently near the surface at high water to act effectually, 
and yet not so near as to be visible at low water. By the 
use of large charges, with a proportionately large radius of 
explosive effect, this might probably be done except in 
extreme cases : and where it would be impossible to keep when ueC es- 
theui absolutely out of sight, the mines and circuit-closers cuu-cioYers, e &c.~ 
might be covered with sea-weed, or disguised in any suit- ° 
able way, in order to conceal to the utmost their real nature. 

In all cases, and in this especially, dummies should be use of fam- 

' mies. 

freely used to perplex an enemy and conceal the position of 
the real, mines. These dummies should bear a close resem- 
blance to the real article, should only be sufficiently conspic- 
uous to attract attention, without revealing their real char- 
acter, and might be placed in any convenient position, or 
even occasionally shifted at night, so as to increase the 
delusion and perplexity. 

A mushroom anchor is in most cases, and especially on a Extempori z e d 
soft muddy bottom, the form which seems best adapted for mc 
mooring submariue mines. Such articles may not, however, 
always be at hand, and it may become necessary to use some 
extemporized arrangement. That shown iu Tig. 25, and 
consisting of a strong heavy wooden *^ 25 

shaft with a number of wooden arms 
or flukes was, after experiment, con- 
sidered a very good form by the 
authorities of the United States of 
America. This might easily be made 
wherever hard-wood timber is avail- 
able. 

Again, the wooden weighted plat- 
form of the Austrians is one that 




anclio 



84 

might be easily constructed in many cases. It seems par- 
ticularly applicable where a charge is to be moved over a 
rocky bottom or bad holding- ground, where it must be kept 
in position by the dead-weight of the arrangement. The 
wooden platform affords a broad space on which any num- 
ber of heavy weights can be conveniently placed and the 
materials of which it is formed, viz, wood and irou, are pro- 
curable everywhere. The system of mooring by these cables 
seems objectionable, as, with a current, they would be very 
likely to become twisted together $ but there is no reason 
why a single cable from the center should not be adopted 
if proper inecautions to strengthen the connection of the 
central point, to which the cable would be attached with 
the outside by means of iron stays, or in some other manner, 
were used. 

qrdina ry It is unnecessary to describe how ordinary anchors may be 
used for mooring submarine mines. 

Large* stone*, Large stones, pigs of ballast, or any heavy weights may 

&c, for mooring be used where the more appropriate forms of apparatus can. 

not be obtained. These must necessarily be sufficiently 

heavy to hold a mine in position by their simple dead-weight- 

^weight of moor ^ vei y important point for consideration, is the weight 
of the anchor or mooring apparatus necessary to hold any 
given size of charge in position. This will depend on its 
buoyancy, and the strength of the current in which it is to 
be moored, and also on the nature of the bottom or holding- 
ground. 

The Austrians recommend very heavy moorings — as much 
as seven times the weight of the charge of powder in cer- 
tain cases. 

This was necessary, because the Austrians always hauled 
a buoyant charge down to its proper position after its moor- 
ings had been placed. The large excess of weight acted 
against the strain in hauling-through the block, which 
was, of course, equal to that of the buoyancy on each por- 
tion of the rope, or double on the whole. Without a con- 
siderable excess of weight, we have found that, during the 
process of hauling down, the moorings are very liable to be 
drawn out of position. 
calculation of ^ s however, the tendency to move depends on the amount 

weight of moor- 7 ^ L 

ings. of buoyancy, the pressure exerted by the current, and the 

tenacity or otherwise of the holding-ground, the weight of 
anchor or mooring apparatus necessary to overcome that 
tendency to move may be calculated as follows : Let JJ be 
of the buoyancy, or excessof flotation over weight of a charge 
of a given submarine mine; let I' be the pressure exerted by 



85 

any given current on the same mine when moored to the bot- 
tom and floating freely therein, it is evident that the result- 
ant of these two forces, or V \\- _j_ W gives the force tend- 
ing to move the mine out of its position.. Now, suppose a 
case where the water is absolutely still, P becomes nothing, 
and the force tending to move the mine would be simply 
equal to B, the buoyancy, and that force would be exerted 
in a vertical direction. To balance this we should require 
an effective weight exactly equal thereto, and taking into 
consideration the necessity of providing an excess in order 
to keep the mine stationary, it would be necessary to at 
least double such weight in practice. In calculating the 
weight to be opposed to the flotation in order to keep a given 
mine from drifting out of position in consequence of the action 
of a current, the effective value of the anchor or moorings 
must be taken as its weight, minus the weight of water dis- 
placed by it. The loss of weight by immersion would, of 
course, depend on the bulk of the mooring apparatus to which 
the mine is attached, and, when this bulk is considerable, it 
becomes a most important consideration in the calculation ; 
when a simple iron mushroom anchor is used, it is probable 
that its weight, if double the buoyancy, would be amply 
sufficient in perfectly still water. Again, let W be the 
weight of mooring required; if the foregoing conclusions 
are correct, we should then have 

W=2 V W+ P 2 

In still water, where P = 0, W would be equal to 2B, or 
double the buoyancy as already assumed to be sufficient. 

Where it is intended to haul a mine down to moorings 

previously placed, more than double the buoyancy would be 

necessary, for the reasons already given. 

A very important element in the above is the amount of Amount 

buoyancy. 
buoyancy necessary to be given to a buoyant mine, and here 

again we must start from some kind of assumed basis, and, 
from the experience we have had in mooring operations in 
the Med way, it would seem that, even in still water, the 
buoyancy should not be less than the weight of the charge 5 
and where a current exists it should not only not be less 
than the weight of the charge, but should be not less than 
three times the force exerted in the form of lateral pressure 
by that current. For example, if it were required to move 
a 500-pound charge in still water, it ought -to have a buoy- 
ancy of 500 pounds as a minimum. 3S~ow, suppose it to be 
subjected to a lateral pressure due to a current of four 
knots an hour, which, on a cylindrical curved surface, may 
be put down roughly at 300 pounds for the size of case which 
would be required for a 500-pound charge, it should then 



Excess over cal 
culated buoyanc 



86 

have a flotation of not less than 900 pounds. In calculat- 
ing the pressure exerted by a current on a cylinder, assum- 
ing the curved surface to be presented to it, half the pres- 
sure which would be exerted on a flat surface equal to its 
greatest sectional area may be taken ; this will be near 
enough for the purpose. We have assumed the buoyancy, 
in the case where a current exists, as equal to three times 
the pressure exerted by that current, in order that the mine 
may not be moved far out of a central position, vertically 
over its moorings, such motion being limited by the direc- 
tion of the resultant of the two forces acting on it ; when 
the mooring- cable is very short, however, this buoyancy 
may be considerably reduced. In any case when a buoyant 
mine is to be retained within certain limits, when moored 
with a given length of cable and acted on by a known cur- 
rent, it is a very easy matter to calculate the buoyancy 
necessary to produce the required result. 

An excess of buoyancy over the calculated amount is 

necessary. " always necessary to obviate the ill-effects of slight leakage 
or any other disturbing cause which might tend to reduce 
efficiency. It is probable that an addition of one-fourth 
would be sufficient in cases where the conditions are favor- 
able, but more may be added where imperfect or make- 
shift arrangements are employed. 
Muddy bottom The deductions to be derived from the above statement 

mooring opera- are applicable only to cases in which the bottom is hard, 
and the mine must be held in position by the simple dead- 
weight of the anchor or mooring apparatus to which it is 
attached. When the bottom is soft this weight may be 
considerably reduced, and in an extremely soft muddy bot- 
tom like the Medway, it is probable that three-fourths of the 
weights, calculated as above, would be sufficient, especially 
where an anchor of the mushroom form is used, this form 
being very applicable to such situations. 

A 10-cwt. mushroom anchor, left for three or four weeks 
at the bottom of the Medway, was found to have sunk com- 
pletely into the mud, and it required very strong tackle and 
a mooring-lighter to weigh it. 

To facilitate search by a diver for an anchor at the bottom 
of a river, it has been found a good plan to paint it white. 
Calculation of In order to calculate the lateral pressure exerted on any 

lateral pressure. . . . ' 

mine by a given 'current, the following formula may be used : 

P = 4.085 x V 2 
where V = velocity of the current in miles per hour. From 
this equation P will be found in terms of pressure in pounds 
per square foot of flat surface, which is, as already stated, 
nearly double that on the curved surface of a cylinder. 



CHAPTEB VI. 

MODE OF IGNITION. 

Having determined on the form of case, size of charge, 
and mode of placing submarine mines in position, it next 
becomes necessary to decide how they shall be ignited so 
as to do as much damage as po'ssible to an attacking ship. 
This may bo done either mechanically or by electricity. 

First with regard to the mechanical mode of ignition. Mechanical igm- 

° lion 

Several arrangements have been tried, with more or less suc- 
cess, by which charges of powder may be ignited by mechan- 
ical action. In several of the confederate torpedoes, which 
were raised from the bottom of the, James River at Rich- 
mond, and the drawings, and some of the originals of which 
I had an opportunity of seeing, through the kindness of 
Brigadier-General Michler, of the United States Engineers, 
a simple gun-lock and percussion-cap were used. These may Slmple s ualock - 
be considered as among the most primitive contrivances of 
this nature, and, from various circumstances, sucli as oxida- 
tion or incrustation in the metal in the more delicate parts, 
perhaps the least likely to act at the right moment. An 
improvement in this was the simple percussion system, by 
which a charge was ignited by the vessel herself striking 
directly on a cap containing a detonating mixture; the most 
delicate of these, mentioued by Captain Harding Steward 
in his notes on submarine mines, appears to be Brook's fuse, Brooks fuse. 
which was arranged in the form of a nipple projecting from 
the case containing the charge, formed of copper of differ- 
ent thicknesses, according to the amount of sensitiveness 
to be given, and priuied with fulminate of silver. The de- 
tails of this fuse are given in Captain Harding Steward's 
paper already referred to, and need not therefore be repeated 
here. Several other forms of detonating fuse were also tried 
by the confederates, both for land and submarine service. 
An account of several ideas for mechanical ignition, devised 
from time to time, may also be found in the report of the com- 
mittee on active obstructions. 

Another mode of mechanical ignition used by the con- sulphuric acid 

n -i t • -.,,, .^ . ., , „ „ or chemical fuse. 

lederates, and previously by the Russans m the defense of 
the ports in the Baltic, is the well-known sulphuric-acid 
fuse, formed on the principal of ignition by sulphuric acid 
dropped upon a mixture of equal parts of chlorate of potash 
and loaf sugar. The sulphuric acid was placed in a small 



88 

glass globule, which was so arranged as to be broken by a 
blow which would be given on touching the side of a ves- 
sel, and the acid set free, falling on the mixture of chlorate 
of potash and loaf-sugar, produced the required ignition. 

Captain Harding Steward gives an account of the attack 
of the United States frigate Minnesota by the confederate 
torpedo-boat Squib, in which Captain Davidson, who was 
in charge of the latter, attributes the partial failure of his 
attack to the slow ignition produced by the chemical fuse 
(sulphuric acid, chlorate of* potash, and loaf-sugar) used ; 
he supposes that, in consequence of this comparatively slow 
ignition, the torpedo-boat had recoiled 3 or 4 feet before the 
actual explosion took place. 
improved chemi- There is no doubt that ignition by the sulphuric-acid fuse 

calfuse. ° ° L 

is comparatively slow — that is to say, slow as compared with 
that of gunpowder; b.ut it may be very much improved by 
the addition of a small quantity of ferro-cyanide of potassium 
or sulphuret of antimony. From experiments made in the 
chemical laboratory at the School of Military Engineering, 
Chatham, it has'been found that an addition of one-third of 
ferro-cyanide of potassium to the mixture of equal parts of 
chlorate of x^otash and loaf-sugar, produces an ignition as 
rapid as that of gunpowder. 
•sodium or potas: Another very simple mode of producing ignition has been 
suggested by Captain Campbell Hardy, of the Eoyal Artil- 
lery; it is simply caused by dropping water upon the metal 
sodium, when ignition takes place. Potassium would also 
answer the purpose, but is inferior to sodium, the latter having 
a greater affinity for oxygen. Captain Hardy made several 
experiments with this substance at Halifax, Nova Scotia, 
Avith good results ; the only fault he found with it was its 
comparatively slow ignition, which, however, he thinks 
might be improved by piercing the body of the sodium with 
small holes. It would be well worth while making a few 
experiments with this substance, for even it* the results ob- 
tained from it are not so good as those of the more approved 
form of chemical fuses, it is so safe to handle that it presents 
many advantages which might be brought into use where 
other forms are not obtainable. The metal sodium can now 
be procured almost everywhere, in the form of a paste, which 
is easily cut and manipulated. It must, however, be pre 
served in naphtha or some substance containing no oxygen, 
or it would soon absorb oxygen from the air and become 
useless as an explosive agent. 
Abeis torpedo- The following description of an adaptation of the sul- 
primer. phuricacid fuse, arranged by F. Abel, esq., F. II. S., chem- 




Fig. 26. 



cu 




Y///firWA 

Cb 




89 

ist to the war department, has beeu approved by the 
floating obstruction committee, and is extracted from 
their report : 

" In Fig. 26, (a) shows the socket to receive the primer, 
which is arranged to be fixed firmly on to the case contain- 
ing the charge, as shown in Fig. 27 ; (b) is the powder-cham- 
ber to hold the priming charge ; (c) is a screw-nut closing 
the powder-chamber ; (d,) Fig. 27, a flexible India-rubber 
tube ; (e, e) are screw-bands ; (/) a lead tube containing the 
explosive mixture; (g) a glass tube containing oil of vitriol ; 
(h) eye to receive the tiring line; (t, i) guard in segments ; 
(j) guard ring , (k) a screw pin." 

"Before the charge is placed in position, a cord or wire is 
attached to the eye of the guard-ring (j), and the screw-pin 
(ft) in the side of the guard-ring is removed. When the 
primer is to be rendered active, after it has been placed in 
position, the guard-ring (j) is removed by pulling the cord 
attached to it. When this has been accomplished the 
guard (t, i) will fall away from the primer, leaving it active. 
The safety-guard of the primer is on no account to be re- 
moved until the mine has beeu placed in the position assigned 
to it. When a sufficient strain is put upon the eye (h) the 
lead tube (/) bends and the fraction of the glass tube (g) is 
thus determined, whereupon the primer is fired." 

The socket («■), Fig. 26, which is to receive the primer, Primer-socket, 
and which accompanies it in the packing-case, is fixed by 
means of screws or rivets into the opening of the vessel 
which is to be converted into a submarine mine. The usual 
precautions are to be taken to make the junction between the 
socket and the case water-tight. A piece of iron-rod, about Fan- lead. 
twelve inches long, is bent at the end into the form of an 
eye ; the other end is then screwed or driven into the case, 
in such a position that the rod is parallel to the primer when 
the latter is inserted in the socket, (as shown in Figs. 28 and 
29.) In this operation, care is necessary to prevent the rod 
being so driven or screwed into the case as to cause leakage 
under the pressure of water after submergence. The dis- 
tance between the rod and the primer should be about six 
inches, and the eye of the rod should be about twoincheslower 
than that of the primer. The nut at the base of the primer charging primer. 
(Fig. 27) is removed, and the powder-chamber (b) is filled 
with gunpowder. The nut is then replaced and screwed 
down tightly by means of the spanner provided for that 
purpose. The charged primer is screwed down as tightly 
as possible upon the washer by means of the spanner. The 
position of the fixed primer is shown in Fig. 27. The firing Firmgiine. 



90 

line is passed thorough the eye of the rod, and is then firmly 
attached to the eye of the primer. (//.) as shown in Fig. 28. 
For this purpose the line must be passed through the hole 
in the guard provided in it, in order that the guard-ring 
may be pulled away after the charge is under water. The 
connection of the firing line with a jack-stay or with the 
line of another mine, may be accomplished either before or 
after it is attached to the primer. A wire of copper or iron, 
or a small line coated with wax or pitch, sufficiently long to 
reach to the surface of the water, after the charge has been 
placed in position, is attached to the eye of the guard-ring. 
The loose end of the wire should be attached to a small float, 
so that it may be recovered at any time. When the mine 
is ready to be submerged, the small pin (Jc) in the side of the 
guard-ring is removed. This pin is not essential to the 
security of the guard, and may, therefore, if thought advisa- 
ble, be removed earlier. It is only provided to prevent the 
guard-ring being removed by persons who may be needlessly 

Lubricating meddling with the primer. If it is intended to leave the 
guard nng. guard upon the primer some considerable time after it has 

been laid down, it will be advisable to lubricate the bearings 
of the guard upon the ring. For this purpose the screw-pin 
is removed, the lubricating agent (grease or oil) is applied 
between the guard and the ring, and the latter is then 
twisted round two or three times, so as to insure the lubri- 
cation of the bearings. This should be done, in every in- 
stance, before employing the primers, if they have been in 

Removal of store for some considerable time. Whenever it is intended 
to render the mine active, the guard-ring is removed by 
pulling the cord or wire attached to it; the guard will then 
fall away from the primer. By bringing the guard-ring to 
the surface the operator will, therefore, know that the mine 
is in working order. 

Different modes This primer may be arranged for the ignition of a mine 

of arrangement for . 

use with a mim. at will from the shore, as shown in Fig. 30; or by the con- 
tact of a passing vessel, as shown in Fig. 28 and 29. 

This form of fuse is now an article of military store, and 
may be issued on requisition. 
Detects ot me- The great defect of all forms of self-acting mechanical 
fuses, is the danger, almost inseparable from them, of acci- 
dental ignition ; a blow given by accident in handling these 
affairs may produce a most disastrous explosion, and there 
is consequently a considerable amount of danger to be 
incurred in placing them in position, and still more in clear- 
ing them away. In the form recommended by the floating 
obstruction committee, security is to a certain extent ob- 



chanical fus 



91 



tained by the metal coverings, which are not removed till 
the charge is actually in its place. Another method by 
which this very desirable object is to a certain extent 
attained, has been suggested by Captain Harding Steward, 
JR. E., pf which the following is a description: 



It consists in the introduction of a stop-cock (A-), Fig. 31, Captain Harding 

n ° Steward's safety 

stop -cock for n:e- 
chanical sub-ma- 
rine n 




Fig 




r 



M 



* 



at the head of the tube, between the fuse and the charge. 
This is so arranged that when the cock is turned in the di- 
rection of the tube, as in section (/), the gas, on formation, 
can pass freely through and fire the charge. When the 
cock is shut off, the gas, on a fuse exploding by accident, is 
made to escape by the side as at (hi), a cut at right angles 
to the main cut in the cone being provided for that pur- 
pose." 

Destruction from leakage of water is one of the chief 
dangers to which this arrangement would be liable, when 
the stop-cock is turned off. It is to be observed, however, 
that it would only be turned off when at or near the surface 
of the water, where the pressure is least, and turned on 
when submerged and the water-pressure greatest, the chance 
of leakage being, however, least under corresponding cir- 
cumstances. In order to prevent the leakage in question, 
Captain Steward has made the following provision : 

•'The cone, in connection with the stop-cock, should be 
ground to fit very accurately, in order to prevent leakage 
of water; and in addition, Captain Steward proposes to 
cover the escape-hole with a small water-proof plaster, which 
at a moderate depth, where the pressure of the water was 
not too great, would keep the water out, while at the same 
time it would offer no material resistance to the exit of the 
gas if the stop-cock were turned off for safety. 



92 

"It is presumed that mechanical submarine mines would 
have guards or covers of some sort to protect the fuses, and, 
with the stopcock in addition, which guarantees cutting off 
the priming from the charge, a detonating mine, however 
delicate, could be transported in a boat to the point of de- 
posit, buoyed on the surface, and the moorings properly reg- 
ulated for submerging without incurring any danger of an 
explosion. The fuse-guards would probably have to be 
removed prior to launching the mine over the side of the 
boat, but the stop-cock could be left turned off till every- 
thing was ready for submerging; until then no greater mis- 
hap than the destruction of a fuse could occur, even if acci- 
dentally struck.' 7 

A few experiments have been made in the School of 
Submarine Mining at Chatham with this arrangement, and 
it was found to cut the gas off from the charge quite effi- 
ciently in every case. 
captain stew- Captain Steward suggests, as a further preventive against 

ard's mode of * too .' , , , , „ , 

mooring mechani- accident, that "three moorings should be used for buoyant 
mechanical submarine mines. If two moorings were, in the 
first instance, established at low water, the case might be 
allowed to float, as shown at (a), Fig. 32; a third mooring 
should then belaid out in the direction of the current, and 
the mine drawn down thereto, which would bring it into 
the position shown at (6), Fig. 32." It is to be observed 
that this mode of mooring (with three cables) is not so objec- 
High water Une>. 

Fig. 32. 
Low w cuter biuy. 




Cb 



tionable with a mechanical mine as it would be with one 
fired by electricity. There being no electrical cable in con- 
nection with it, to be wound up or injured, no necessity ex- 
ists for preventing it turning to any extent, and it might 
be supplied with a swivel at its apex to admit of its turning, 
as is often done with ordinary buoys. 

" To raise a mine thus deposited the case could be brought 
to the surface, at low water, by raising the stream mooring 
and bringing it forward a little.' 7 



93 

On raising a mine it might be made quite sale by simply 
turning off the stop-cocks the moment it came to the sur- 
face. 

This arrangement for shutting off, as it were, the fuse 
from the charge of powder, is applicable to almost any form 
of mechanical ignition that may be devised. 

Passing from the mechanical we now come to the elec- .Electrical ign 

° tion. 

trical mode of ignition, in which a very important matter 
for discussion is the fuse. 

Several forms of electrical fuses have been devised and 
used for the ignition of gunpowder, gun cotton, &c. The Piatinum-wiro 
confederates used the platinum- wire fuse and Grove's or 
Bunsen's battery in many of their mines, which were ar- 
ranged to be fired by electricity. This form of fuse, in con- 
nection with the first-named battery, has for a long time 
formed a part of the engineer equipment of the British 
army for land-mining operations, and the result of some 
experiments with it, in connection with submarine mines, 
have been so successful that it is to be hoped that it will 
satisfactorily fulfill the necessary conditions for the latter 
jHirpose. 

There are numerous advantages to be derived from the , Advantages of 

° tne platiuum-wiro 

use of the platinum-wire fuse, of which the following are ft««- 
the principal : 

1st. Great facilities are afforded for testing the circuits. 

2d. It does not deteriorate by climate, &c, and can be 
stored for any length of time without damage. 

3d. It can be very easily improvised, and the materials 
of which it is composed are simple. 

Ith. It does not require the very high insulation in the 
conducting cable which is necessary when a fuse, fired by 
a current of high tension, is used ; and it may be fired 
through a cable in which a comparatively large fault exists. 

5th. There is no danger of an accident during the pro- 
cess of testing, for which purpose more powerful batteries 
may consequently be safely used. Considerable care is ne- 
cessary in testing Abel's fuses, for example, as more than 
one of the most sensitive form has been fired by eight 
small Daniells cells. 

It has been ascertained by experiments carried on in the 
river Medway, opposite Gillingham, that in sea-water a re- 
turn-wire is not necessary, and that even earth-plates of 
any considerable size are not essential when using this fuse 
in connection with Grove's battery; fuses having been suc- 
cessfully fired with earth connections formed of a few inches 
only of bare wire, with the addition of a comparatively 



94 

small number of battery cells over the number necessary 
with a return-wire or ordinary earth-plates. 
whhyaunumfuse Tbe following is a short account of the experiments tried : 
and Grove's bat- ^ platinum fuse, represented" by j\ inch of platinum 
wire, in a thermogalvanonieter, was placed in circuit with 
half a mile of a cable, composed of Hooper's core, with a 
conductor consisting of a strand of 7 No. 22 B. W. G. 
copper wires, and without a return-wire. One pole of the 
battery was connected by a short length of No. 12 B. W. 
G. copper wire, with the copper sheathing of the mooring 
lighter, the outer extremity of the cable being soldered to 
a tin case 2 feet 6 inches high, and 2 feet inches in diam- 
eter, to form the other earth connection, this tin being about 
100 yards from the lighter. With this combination 7 3 y 
inch of platinum wire, weighing l.G grains to the 
yard, were fused with six cells of Grove's battery of 
the ordinary military pattern. A second half mile of a 
similar cable having been added to the conductor, 7 \ inch 
of platinum wire were fused with eight cells; on a third 
half mile of cable, making in all 1J miles of conductor,, 
being added, the platinum wire fused with 13 cells. 

In order to ascertain whether an increase of distance be- 
tween the earth-plates in any way altered the conditions of 
Distance between the case, the tin can, forming" the outer earth-plate, was 

earth-plates,insea- 7 x 

water, no objec- moved to a distance of rather more than 500 yards from the 
lighter, and connected with 1J miles of conductor as before, 
the electric cable being moved out for this purpose; with 
this combination T % inch of platinum wire were fused with 
12 cells, and in a second trial with 13 cells of the battery, 
thus proving that there was no additional resistance inter- 
posed by the increased intervening mass of water, or, in 
other words, that the water resistance was practically nil. 
Experiments to Further experiments have been tried with Grove's battery. 

determine the min- 
imum of earth con- and the platinum fuse, to determine the minimum of earth 

nection with . . . ' . 

Groves battery connection, requisite effectually to luse the platinum wire, 

e ' without inordinately increasing the number of battery cells.. 

With a conductor, consisting of half a mile of cable, 

(Hooper's core, similar to that used in former experiments.) 

and y 3 ^ inch of platinum wire in a thermogalvanometer 

to represent the fuse, the following results were obtained : 



Number of cells to produce fusion. 

G 


Extent of earth in inches of bare wire 

24 


7 


15 


8 


6 


9 


3J 


10 


•> 



95 

One pole of the battery was on this, as on the former oc- 
casion, attached to the copper of the vessel as an earth- 
plate. 

With on mile of conducting cable in circuit and similar 
arrangements to the above, the following results were ob- 
tained : 

Number r,(' cells to produce fusion. Extent of earth in inches of bare wire. 

20 f 

20 J 

The latter failed to fuse, but heated the platinum wire to 
redness. 

The result of these experiments show that earth-plates of 
the ordinary size will answer every purpose, when used in 
connection with Grove's battery and the platinum fuse for 
submarine mining purposes. 
Mr. Brown, of the chemical department, royal arsenal, increase of fusing 

' ■ power produced 

gives the following information, as the result of some ex- by the sudden re- 

f ' versa! of the poles 

perminents made by him with Grove's battery and the pla- ofaoattery. 
tinum fuse. He finds that the best results were obtained 
by suddenly reversing the poles of the battery; that is to 
say, that a fuse which will not lire with a given number of 
cells of a battery may be successfully fired by simply revers- 
ing the poles of the same battery. The reason of this is 
that, by keeping one pole of a battery constantly on, copper 
earth-connections, which are the best for general purposes, 
become coated either with sub-chloride of copper or with 
bubbles of hydrogen, both of which partially insulate. A 
sudden reversal of the poles of the battery dissipates these 
combinations for a time, that is to say, till they again form 
by changing places, as it were, on the opposite earth-plates, 
to those on which each was originally deposited. A similar 
effect is produced whatever may be the metal of which earth- 
plates are composed ; that is to say, a film of hydrogen bub- 
bles will be deposited on the earth-plate attached to the 
negative, or zinc, pole of the battery and a film of sub- 
chloride of the metal on that connected with the positive 
or platinum pole, both the result of the decomposition of 
sea-water by the electrical current. 

A platinum-wire fuse has been designed for submarine Form of plati- 
num fuse for sub- 
mining purposes, which, as far as it has been at present marine mining 

tried, seems to answer satisfactorily. It consists of a couple 
of copper wires of Xo. 16 B. W. G., fixed into an ebonite 
core («), as shown in Fig. 33, and the opening through 
which they are introduced made thoroughly water-tight by 
filling it with water-proof composition. It w r as found im- 
possible to cast the ebonite directly on to the bare wire, 



96 

which would have been a much more satisfactory arrange- 
ment, because the sulphur of the ebonite acted power- 




fully on the copper conductor and destroyed it. This 
core is provided with a shoulder (d) to enable it to 
be fitted into the case in such a manner as to pre- 
vent leakage of water. The extremities (c c) of the copper 
wires are T 3 inch apart, and so arranged that a thin pla- 
tinum wire may be easily soldered on to connect them and 
form the bridge of the fuse. A cap (d) screws on to hold 
the priming charge and protect the bridge (c c) of the fuse ; 
and in this cap is a loading-hole (e) to introduce the prim- 
Priming. j U g. The priming may be either ordinary gunpowder, gun- 

cotton, or, when the fuse is to be made detonating, in order 
to produce the effect due to this mode of ignition, fulmi- 
nate of mercury, which latter must be inclosed m a strong 
case in order to produce detonation at the moment of igni- 
tion. For this purpose the whole cap (d) may be made 
strong. 

The outer terminals (//) of the copper wires are insulated, 
and arranged for attachment to the electric cable and to 
earth ; a circular opening, (g 7t,) four inches in diameter, is 



f 1.1 -It. 



97 

left in the case (/ i) of the mine, for the purpose of intro- 
ducing' the charge. The opening is made four inches in 
diameter to allow gun-cotton, in the form of disks, to be 
introduced, if it is desired to use this explosive. This open- 
ing is provided with shoulders at (g) and (7i), on which the 
corresponding shoulder (b) of the fuse fits, and the latter is 
forced down, by means of a circular screw, (A:,) fitting into a 
corresponding screw in the opening of the case, (i.) This 
forces the shoulder of the fuse down upon a ring of India- 
rubber packing, (I,) shown in black in the section, and makes 
all water-tight. 

Gun-cotton priming has the effect of rendering the fuse (inn-cotton 

priming- forms a 

more sensitive than gunpowder, as it ignites at a much lower 
temperature, as maybe seen from the following experiments 
tried by Lieutenant Bucknill, E. E. With a conductor of 
one and one-half miles of cable, (Hooper's core, as previously 
described,) and ordinary platinum fuse, as made in the 
school for land mining, primed with gunpowder, fired with 

12 cells of Grove's battery, and the platinum wire fused with 

13 cells. The fuse, Fig. 33, designed by Lieutenant Buck- 
nill, was next tried. With the same cable, (one and one-half 
miles) — 

Gun-cotton priming fired with . . . . : 6 cells. 

Mealed powder fired with 11 cells. 

Cotton and powder mixed fired with ............ 7 cells. 

With one-half a mile of conductor, the following results 
were obtained : 

Gun-cotton priming fired with 2 cells. 

Mealed powder fired with 4 cells. 

Cotton and powder mixed fired with 2 cells. 

With the same cable (one-half mile) and a leak of one 
foot of bare wire in the conductor — 

Gun-cotton priming fired with 4 cells. 

Mealed powder fired with 7 cells. 

With the same cable (one-half mile) and a leak of 2 feet 
of bare wire — 

Gun-cotton priming fired with 5 cells. 

Mealed powder fired with 8 cells. 

With a conductor of one mile of cable and a leak of 2 feet 
of bare wire — 

Gun-cotton priming fired with . . 9 cells. 

Mealed powder fired with 15 cells. 

In one case of mixed powder and cotton the powder did 
not surround the cotton, and the latter ignited without 
firing- the former. It is thereftra necessary to imbed the 
7 



98 

cotton well in the priming-powder, and no failure has ever 
occurred when this was properly done. 
Electric battery In order to fire a charge by means of the platinum-wire 

for use with plati- . l 

numfuse. fuse, a battery producing a current ot large quantity must 

be employed, ignition being produced by heating the piece 
of fine platinum wire in the circuit to fusion, by the pas- 
sage of the electric; circuit Grove's, Bunsen's, Walker's, or 
Smee's batteries are among those suitable for this purpose. 
Grove's battery. The experiments recorded were carried on with Grove's 
battery, of the form adopted for mining in the British serv- 
ice. A detailed account of this battery may be found in 
Schino's " Notes on Electricity," and the reasons for its adop- 
tion are recorded in an article by Captain (now Colonel) 
Ward, R. E., in the fourth volume of the new series of corps 
papers. 
Detect s of Grove's battery possesses the defect of inconstancy ; that 

Grove's battery. . g ^ ga ^ that, a fter having been in action, or even mounted 
and ready for use, for a comparatively short time, the active- 
force of the current is considerably diminished, and in time 
it would no longer possess the power to fire a platinum 
fuse. From experiments tried at Chatham it has been ascer- 
tained that when used under similar conditions to those for 
which it would be employed as an agent for submarine 
mines, 24 hours is about the limit up to which it will per- 
form its work with certainty. If adopted for this purpose,, 
therefore, it would be necessary to take it to pieces, clean r 
and remount it every 24 hours. 

When this battery remains in a passive state — that is to 
say, not actually in action — it does not deteriorate so rapidly 
as when in constant use 5 and, as in working a system of 
submarine mines, it would only be in action at long inter- 
vals, each of comparatively short duration, it would not be 
so unsuited for the purpose as might, at first sight, appear. 
In consequence, however, of this defect, it would be desir- 
able to obtain, if possible, a constant battery for the pur- 
pose required, and with this view experiments have been 
instituted with other forms of batteries, 
walker's bat. Platinum wire may be fused by means of Walker's zinc 
carbon battery, which has the advantage over Grove's bat- 
tery of being more constant. It may be allowed to remain 
mounted for weeks together, without any considerable re- 
duction in the strength of the working current, and in this 
respect would be preferable for a permanent station. 

Mr. Walker states that he has fused T 3 Q inch of platinum 
wire of 1.95 grains to the yard, with cells of a battery of this 
form, composed of plates2 inches wide and 3 inches immersed 



99 

in dilute sulphuric acid, (1 of acid to 8 of water.) With 7 or 8 
cells the wire is fused better, and with 9 it works very well . The 
plates of the battery used by Mr. Walker are comparatively 
small, and consequently a large number of cells of this size 
is required to produce the same result which would be ob- 
tained from two cells of the service pattern, portable form 
of Grove. In order to test the efficiency of this battery, 
therefore, an experiment was tried in the telegraph- school 
at this station, (Chatham,) by combining together a num- 
ber of plates of Walker's battery so as to form two large cells. 
By arranging in this way so as to obtain an immersed surface 
of 140 square inches of zinc, we were just able, with two cell's, 
to fuse j\ inch of platinum wire of 1.95 grains to the yard. 
This surface of 140 square inches might easily be obtained, 
in a compact form, by giving the plates a cylindrical, or, 
perhaps better, for the more easy manipulation of the car- 
bon, a polygonal form, under which they might be combined 
in a diameter of 4i inches, and height of 8 inches, extreme 
outside measurement, for each element of the battery. A 
few large cells of this form of battery have accordingly been 
procured for experimental purposes, and the results ob- 
tained with them have proved so promising that further- 
investigations are about to be made. 

The platinum-wire fuse is itself very simple and very Electric fuse tor 

"use with current 

easily made at any time; but in consequence of the defects of high tension. 
as regards the battery for use with it, and the apparent dif- 
ficulties in overcoming these defects, efforts have been 
made to produce electrical fuses capable of being fired by a 
current of high tension, in contradistinction to one of large 
quantity, which latter, as produced by Grove's and other 
batteries, is necessary for use with the platinum-wire fuse; 
also keeping in view the necessity of using a constant bat- 
tery. 

One of these, invented by Mr. Beardslee, of Xew York, 1 "-' 
consists of a cylindrical piece of soft wood, about three- 
quarters of an inch in length and about three-quarters of an 
inch in diameter, shown at (a) Fig. 34, through which two 
copper nails (b b) are driven home in a slanting direction, so 
that while the two heads come as close together as possible 
without absolutely touching, the pointed ends are at some 
distance apart from each other, and project below the wooden 
cylinder. To these ends are soldered the bare terminals of 
two insulated copper wires, (cc;) and a piece of soft wax, (cl,) 
of the same size as the wooden cylinder, is pressed around 
the points of junction. A groove is made with a file across 
the heads of the copper nails, into which is rubbed a little 



fuse. 



100 



Vo 

fuse. 



Ebn< 



black-lead from a pencil.* Kound the wooden cylinder 
are now wrapped several folds of paper, forming a cylinder 



£%, 34. 





Fig. 35. 



about 2J inche s in length, one end being tightly fastened 
with a string round the insulated wire at (e.) This paper 
cylinder is then filled with a mixture of very fine grain and 
mealed powder, (/,) and the end (g) is choked with twine. 
The entire fuse is afterward coated with black varnish. 
Another fo rm of electrical fuse is the Austrian, invented 
by Baron Von Ebner, of the Austrian 
engineers, which is shown in Fig. 35. 
It consists of an outer cylinder of 
INn! 1K3I gutta-percha, covering an inner core 

(c?,) composed of a mixture of sulphur 
and ground glass, cast round the con- 
ducting-wire, which is, in the first in- 
stance, in one continuous length, the 
opening (e) being subsequently made 
and carefully gauged, so as to secure 
a uniform break or interval in the conductor of each fuse. 

The fuse composition consists of equal parts of sulphuret 
of antimony and chlorate of potash, to which is added a 
small quantity of powdered plumbago, the latter to give a 

* A minute quantity of some substance which importantly assists the 
black-lead in its action is applied to the wood in addition to the black- 
lead in the fuses of Mr. Beardslee's own manufacture. The nature of 
this substance has not been disclosed. 






101 

certain amount of eonduetiug power to the composition for 
testing purposes. This mixture is put into the hollow (f) 
of the fuse under pressure, the terminals being connected 
with a very sensitive galvanometer in circuit with a small 
battery during the operation of filling, and the pressure 
applied so as to obtain, as far as possible, a uniform 
electrical resistance in each fuse. 

A very similar fuse to this, in fact almost identical, and Prussian fuse. 
only differing in form, is used by the Prussians for mining 
Fig. GG. purposes $ this is shown in 

Fi g. 36 ; (g) is a small cylin - 
der of hard wood, through 
which a conducting wire is 
drawn to the hollow space 
(//) in the center. Similar 
precautions to those adopt- 
ed in the Austrian fuse 
WM/mtf/ y/M ${ are taken in making and 

gauging the break in the conducting wire, and in filling 
in the composition, which is the same as that used by Baron 
Yon Ebner. The opening is stopped with a cork, shown at 
(i) in sketch. 

Of these two last forms the Austrian seems to be the best, 
being less likely to be damaged by a sudden strain or tug, 
which might easily alter the interval between the points of 
the conducting wires in contact with the fuse composition 
in the Prussian fuse. 

Another similar form of fuse is that invented by Mr. Abel, Abel's fuse. 
chemist to the war department. This fuse was devised 
and experimented with extensively in 1858 5 and the above 
more recently designed fuses (viz, Beardslee's, the Austrian, 
and Prussian) are based upon the principles first applied in 
that fuse. It has been modified since its first invention in a 
few details. Fig. 37 shows its most recent form. The prim- 
ing of the original fuses consisted of 10 parts of subphos- 
phide of copper, prepared by a special method, 45 parts of 
subsulphide of copper, and 15 parts of chlorate of potassa ; 
these proportions of the ingredients are, however, now varied, 
so as to furnish fuses of different degrees of conductivity 
and sensitiveness to suit different purposes. The ingre- 
dients are reduced to a very fine state of division, and are 
thoroughly incorporated in a. mortar, with the addition of 
a little alcohol : the mixture is then dried at alow tempera- 
ture, and preserved in tightly-stoppered bottles till required 
for use. This composition is very sensitive as an electric 
priming material, and is perfectly stable so long as it is 



102 



preserved from access of moisture. This condition, essen- 
tial to the permanent efficiency of the fuse, is secured 



Fig, 37, 





by the present form of construction, and the precautions 
adopted in packing such warlike stores as friction- tubes, 
time-fuses, &c, suffice to insure the preservation of these 
fuses. 

In applying the electric spark to the explosion of fuses, 
the distance from each other of the metallic points, between 
which the spark passes, must be adjusted with great nicety : 
and it is also important, Avhen a number of charges are to 
be exploded in divided circuit by means of a magneto- 
electric machine, that no residue should be left between the 
poles after the explosion of the fuse, which would still serve 
to conduct the spark across the interval. The composition 
discovered by Mr. Abel completely fulfills the latter condi- 
tion, and the former is ingeniously secured by the form of 
fuse adopted, and hereafter described, which is now an 
article of store obtainable at the royal arsenal, AVoolwich. 
^Construction of interring to Fig. 37, (b b) is a body of beech-wood, hol- 
lowed for half its. length for the reception of the bursting- 
charge, and perforated by three holes, one vertical, for the 
reception of the capsule of sensitive mixture, and two hor- 
izontal, to receive the conducting-wires; (a a) are two insu- 
lated copper wires introduced into the vertical perforation 
in the body, and resting on the sensitive mixture ; (d) is a 
small charge of mealed powder contained in the cavity of 
the fuse, and fired by the ignition of the sensitive mixture. 



103 

The insulated wires are prepared for these fuses in con- 
siderable lengths. The}' consist of copper wires of 24 
gauge, ( = 0.022 inch diameter,) inclosed in a coating of 
gutta-percha 0.13 inch in diameter, and separated about 0.0G 
inch from each other. 

A piece of the double-covered wire, about two inches 
long, is employed in the construction of the fuse. The 
gutta-purcha is perfectly removed from about 1.25 inches 
of each wire at one end, aud the other extremities of the 
wires are furnished with clear sectional surfaces by care- 
fully cutting the double-covered wire across with sharp 
scissors, care being taken that the ends of the wires are not 
pressed into actual contact by this operation. 

A small quantity of the priming composition is put into 
a small cylindrical paper-cap, (c, c,) made to fit the double- 
covered wire. The prepared piece of the latter is then in- 
serted into this cap, and the exposed sectional surfaces of 
the wires are firmly pressed down upon the composition, so 
that the latter becomes compressed ^into close contact with 
them. The cap is afterward coated with strong shellac 
varnish. The actual fuse is thus completed, but it has still 
to be fitted in such a manner as to permit of its ready em- 
ployment, and to protect it thoroughly from damp. 

With this view the capped end of the double-covered 
wire is inserted into the perforation (i) in the head of the 
wooden cylinder, so as to project about 0.15 inch into the 
cavity (d) of the cylinder. The bare ends of the wires are 
pressed into small grooves in the head of the cylinder, (e e,) 
and each extremity is bent into one of the small channels or 
eyes (W d') with which the cylinder is provided, and 
which are at right angles to the central perforation. They 
are then wedged tightly into position in these channels by 
inserting into the latter two small copper tubes, (shown in 
outline d' d',) which fit closely into the holes, and are 
driven in over the wire ends, being afterward filed down 
flush with the surface of the cylinder. 

The cavity of the latter is then filled with meal-powder, 
which is tightly rammed down, so that the fuse itself be- 
comes firmly imbedded in it. The opening of the cavity is 
afterward closed by pressing into it a plug of softened 
gutta-purcha, aud, finally, the complete fuse is coated with 
black varnish. 

In order to connect this fuse with the electric exploding 
apparatus, it is only necessary to insert the bared extremity 
of each conducting wire into one of the small copper tubes 
or eyes [&' d') in the head of the fuse, and to fix it there by 



104 

bending, the wire round on to the wood, as shown at & '. Ri- 
gidity is imparted to the connection by twisting or turning 
the wires together over the top of the fuse, as at (/). Per- 
fect contact should be secured by a copper tack used as a 
wedge. 

Before inserting the wires, with the fuse fixed upon them, 
into a charge of gunpowder or other explosive, it is advisa- 
ble to cover the connections of the wires and fuse, either by 
wrapping a piece of gut-skin, oiled canvas, or other water- 
proof material round the head of the fuse. 

The powder for ordinary fuses is contained in the cavity 
of the wooden body, and the fulminate for detonating fuses 
in a cylinder of sheet tin, tightly fitting on the fnse-head. 
Abel's i u s e This fuse is adapted to the electricity obtained by friction. 

adopted for cur- L J J 1 

rents of high ten- or to the momentary induced currents derived from perma- 
nent or electro-magnets, or an induction-coil. It can also be 
ignited by the direct voltaic current 5 about 60 cells of 
Daniells's or 30 cells of Grove's battery being necessary to 
overcome the resistance with certainty, although very deli- 
cate fuses may be fired by 12 cells of Daniells's battery, or 
even less. 

Testing Abei'a AbePs fuses can be tested by passing a weak current of 
three or four Daniells's cells through them, with an astatic 
galvanometer. Each fuse should be thus tested before it is 
placed in a charge. 

Abeis detonat The difference between the detonating fuse (required for 
gun-cotton) and the service electric fuse, consists in the 
substitution of fulminate of mercury for the priming charge 
of gunpowder, and in addition of an external tin casing for 
the bottom of the fuse ; the service electric fuse is painted 
black, while the head of the detonating fuse is painted red. 

Effect of test Having heard considerable doubts expressed as to the 
fuses. ' durability of the composition in this fuse, when subjected to 

the passage of test currents, some experiments w 7 ere made 
at Chatham with a number of them, taken at random from 
our stock, with the result shown in the following table. 
(See page 105.) These fuses were of the old form, possess- 
ing a very high electrical resistance. 

From these experiments it appears that the electrical re- 
sistance of the fuses w T ere not materially altered by the pas- 
sage of a test-current through them, under any of the differ- 
ent circumstances in which it was applied; they all fired at 
the end of the experiments without any failure, and there 
seems to be no danger of ignition when using a test-current, 
provided that current is properly adapted for the purpose. 
A large number of these fuses are used in the course of in- 



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106 

struction giveD in the electrical school at Chatham, and the 
percentage defective is so extremely small that it may be 
safely asserted that Abel's fuse is remarkably well suited 
for the purpose for which it was desigued. It possesses the 
essential quality of certainty of ignition, and is further of 
such construction that its electrical condition can be easily 
and safely ascertained at any time, both before and after it 
is placed in the charge, by means of a test-battery and deli- 
cate galvanometer. 
precautions Some of the fuses most recently made bv Mr. Abel are 

necessary in test- . . " 

mg Abei's fuses of extremely sensitive, and have been fired bv the passage of 
a continuous current, of 6 Daniells cells of the ordinary 
form, in from 4 to G hours and upward. These very sensi- 
tive fuses are no doubt preferable for simple mining pur- 
poses, but it must be borne in mind that they are unsuitable, 
and even absolutely very dangerous, when placed in a 
circuit in which they are subjected to the continuous passage 
of even a very feeble current of electricity, for a compara- 
tively short time. When such a combination is required, 
the less sensitive form of Abel's fuse, that with which our 
experiments were made, must be used, and in fact may be 
used with perfect safety. It must not, however, be supposed 
that these very delicate fuses, above referred to, cannot be 
tested; this maybe done with perfect safety, provided a 
suitable battery and galvanometer is used. It would not 
do, however, to put them in the hands of every one, and 
they should only be intrusted, when used for submarine 
mining purposes, to a most careful workman, who must 
also be an experienced electrician. In using Abel's, or indeed 
any fuses, each should be carefully tested and marked 
previous to being placed in the charge, to avoid the smallest 
chance of ignition in the latter position while testing. 
Extempori zed In certain cases when Abel's or any other manufactured 
fuses may not be attainable, it may become necessary to 
make extemporary fuses for use on the spot. This may be 
done in several ways, which have proved more or less suc- 
cessful. 

For example, a fuse, capable of being used with a constant 
battery of a large number of cells, may be extemporized on 
the principle of Beardslee's, as described in the report of 
the committee on active obstructions, as follows : 

"A small cylinder, Fig. 38, of hard wood or cork, about 
| inch in diameter and f inch thick, is provided with a 
groove (a) round its circumference, and two perforations, 
(h &,) about J inch apart, of a suitable size to receive two 
moderately thin pieces of copper wire, (about IS B. W. 



fuses. 



107 



gauge being a convenient size.) One extremity of both 
of these wires is sharpened with a file and then converted 
into a hook, the head of which is afterward flattened, as 
shown in Fig. 39. 

a The straight ends of the wires are then passed through 
the holes in the cylinder and the flattened 
Mg* 38. heads are fixed in the wood, by driving the 
pointed extremities into the latter. In this 
way the broad, thin metal surfaces which 
form the poles of the fuse are fixed in a 
parallel position on the surface of the wood 
or cork, and should be as close together as 
possible Avithout actually touching. This 
arrangement is shown in Fig. 40. Before, however, the 
wires are thus placed in po- 
sition, the surface of the 





Fig. 40. 



cylinder, upon which 

poles are to be fixed 

brushed over lightly with a 

feather-tip or hair-pencil, which has been dipped into a 

solution of ordinary photographic collodion. When the 

poles have been fixed into the cylinder thus prepared, the 
small surface of wood which inter- 
venes between them is coated with 
graphite by drawing a pointed 
black-lead pencil across it two or 
three times. A cap of thin paper is 
then tied round the cylinder (a,) 
Fig. 41, so as to inclose the poles 
of the fuse ; this cylinder is filled 

compactly with fine-grain gunpowder, and the open end is 

then choked, as shown at (&,) Fig 41. 

"The protruding wires of the fuse (c <?,) Fig. 41, which 

serve to connect it with the conducting wires, are coated 




Fig. 41. 




to within a short distance of their extremities by molding 
ordinary bees-wax round them with the fingers, and then 
tightly wrapping the wax over with thin strips of tape or 
rag of any kind, which is secured. at the ends with thread. 



108 

The entire fuse, except tbe bare ends of the wires, may 
then be brushed over with Brunswick black, or any other 
description of varnish or lacquer which may be at hand. 

u The only material not universally obtainable, which is 
required in the production of these fuses, is collodion, 
which is, however, now so very extensively used, that it 
will/ generally be readily procurable. A small bottle, 
corked or stoppered, containing one or two ounces of collo- 
dion, will suffice for the preparation of a very large number 
of fuses." 

This fuse may be fired by means of a constant battery of 
sufficient power, or by Wheatstone's magnetic exploder, the 
former of which generates a continuous current, and the 
latter a rapid succession of short currents. It would rarely 
be fired by means of a frictional or other machine capable 
of producing a single discharge only, because, in order to 
produce the necessary heating-power, a continuous passage 
of the current through the plumbago-bridge is essential. 
In using this fuse it frequently happens that a short interval 
elapses between the closing of the electrical circuit and 
ignition, this time being required to produce the necessary 
amount of heat alluded to. 
Lieutenat Fish- Another form of fuse, designed by Lieutenant Fisher, 

ers extemporized ' ' 

fase. E. N., is similar in general construction to the above, but 

differs in the composition of the bridge. For plumbago 
Lieutenant Fisher substitutes a mixture of powdered char- 
coal and resin ; this, he states, produces a fuse which tests 
sufficiently well, and is very certain of ignition. The mate- 
rials of which it is composed are so simple and easily pro 
cured that it bids fair to make a very useful fuse, easily 
made where a supply of the more perfect Abel's fuses may 
not be at hand. As, however, the efficiency of a mine de- 
pends very considerably on the quality of the fuse, extem- 
porary fuses should never be used when the more perfect 
forms are attainable. 

> Next, as regards the position in which a fuse may be 
most advantageously placed, and the number required to 
fire any given charge. 

It has been already stated that, in order to develop the 
full explosive effect of even a small charge of powder, when 
fired underwater, a very strong case is required 5 in fact, 
that the maximum effect of a 4-pound charge was not at- 
tained until a case of \ th-inch iron , capable of standing a grad - 
ual pressure from w r ithin of 330 pounds per square inch, was 
used. For large charges, of 500 pounds and upward, it is 
therefore evident that it would be quite impossible to make 



Positior 
in a cbanro. 



109 

cases proportionately strong to secure a similar development 

of explosive effect, because they would become enormously 
heavy. 

We may, however, to a certain extent obviate this effect 
of loss of power, as it were, by igniting the charges when 
of large size, at several points, providing, in fact, several 
centers of ignition, and thus burning as much as possible of 
the charge and converting it into gas, before the envelope 
is broken and the water admitted. 

Let us first consider what would be the maximum charge Maximum charge 
which it would be desirable to fire with a single fuse, suppos- emgi 
ing that in other respects it is favorably circumstanced; that is 
to say, the case being of the best form and of as great strength 
as circumstances will admit, &c. The radius of ignition due 
to a single fuse, when fired under the circumstances above 
described, has not yet been ascertained, but it is supposed 
to be about 1 foot, and, starting with this basis, our maximum 
charge, to be fired from a single center of ignition, is at once 
determined at about 250 pounds. If, therefore, this suppo- 
sition be correct, and we may assume that it is till reliable 
data have been obtained, we must use a single center of ig- 
nition for all charges of less than 250 pounds of powder, 
adding a fresh fuse, suitably placed, for each additional 250 
pounds, or fraction of 250 pounds, in the charge to be fired. 

This has reference to gunpowder fired with an ordinary 
fuse. When gun-cotton and a detonating fuse are used, a 
much greater bulk may be exploded from a single center of 
ignition. 

The distribution and holding in p roper relative position Distribution of 
of a number of fuses iu a large charge of powder is a matter laJJe c^arg? m a 
of some little nicety, and in addition we have the increased 
difficulty of testing the fuses after being placed in the 
charge, and the increased chance of failure and trouble in 
replacing a defective fuse, or adjusting any accidental de- 
rangement of the conducting-wires should a defect occur 
in the heart of the charge itself, which would render the 
emptying out of the case necessary. Iu order to obviate 
these defects, the following very ingenious arrangement 
has been suggested by Captain Harding Steward, B. E. 
The description is extracted from his report : 

" The charge of powder should be packed in an India-rub. captain 
ber bag, about 12 inches in diameter, (internal,) and of a ar( 
length sufficient to contain it j (a bag -12 inches long will take 
a charge of 150 pounds.) 

"For the firing arrangement a brass tube and a fuse 
primed with powder are requisite. The brass tube should be 



110 



sufficiently long to run the whole length of the bag when 
filled and tied at the end, and should have an internal diam- 
eter of one inch. To fit the tube for its object, it is neces- 
sary to cut slits \ inch wide and 1-J inches long at central 
intervals of three inches, and following a spiral line round 
the tube. (See Fig. 42.) These slits should be covered with 
brass wire-gauze, of a mesh sufficiently small to exclude 
powder, and one end of the tube should be closed and the 
other provided with short lugs. 

" A fuse primed with 2 drams of powder, placed in the 
end of the tube and well secured to the lugs, also tightly 




a. 



covered, so that only the wires protrude, completes the ar- 
rangement. It is then put altogether in the central line of 
the charge and secured, so that it shall not vary its position. 



Ill 

k * On applying electricity of a kind suited to the fuse em- 
ployed, jets of gas are driven from all tlie openings in the 
tube. These jets, accompanied by flame or without it, fire 
the powder within their reach, and the result is the complete 
ignition of the outlying portions even before the gas evolved 
by the grains first ignited has time to rupture the case or 
bag and let in the water. 

" The experiments made with this mode of ignition have, 
owing to circumstances, been confined to lighting several 
trains and heaps of powder arranged about the tube, at inter- 
vals sufficiently large to prevent them communicating on one 
being tired. The ignition was in all cases attended with 
perfect success. 

" The fuses employed were of my own making, and suited 
for the electricity of a magnetic exploder. Equally good 
results can be obtained by priming Abel's mining-fuse, or 
his experimental fuse, with two drams of powder, pro- 
vided that the fuse, when packed, fits the tube tolerably 
well. Two drams of powder only are proposed, as with 
three and with four drams it was found that the blast not 
only (in the above experiments) drove away the powder, but 
prevented the emission of gas from the two or three holes 
nearest to the fuse. It is, however, rjossible that with a 
confined charge an increase of the priming might not be 
attended with the above results. If it is thought desirable 
to employ two fuses, so that in the event of one of them 
proving to be bad ignition may be secured through the 
other, the same can be done by arranging two tubes three 
inches apart, connecting their ends in order to keep them 
in their relative positions. 

u The mode of ignition proposed will be found so complete 
that metal cases for torpedoes can be dispensed Avith, and 
barrels used instead, for a water-tight covering is all that is 
required for the charge. 

" The proposed plan is also likely to prove useful in all 
cases in which ignition by means of chemical fuses, or by^ 
detonation, is used ; for the powder, according to existing 
plans, is only ignited at a single point, and that one is close 
to the exterior of the mass of the charge, consequently the 
combustion of the charge would take place under unfavor- 
able circumstances. 

" In the event of the proposed mode of ignition being em- 
ployed for land-mines, it will certainly economize powder, 
but its utility will not be so apparent, for the surrounding 
earth cannot spoil a portion of the charge, as water does ; also, 
that defective ignition can always be compensated for by an 



112 

increase of the charge. The plan, however, permits of the 
series of fuses being dispensed with, which is, however, a 
mode of ignition little used in field-mining operations. 

"With very large charges, (say from 300 to 500 pounds,) the 
following out of the cylindrical form, with a diameter not 
exceeding 12 inches, as recommended, would involve incon- 
veniently long powder-cases. It is therefore necessary to 
subdivide the mass of powder, and to employ branches 
with the tube. This can be best effected by treating a mass 
of powder as made up of a series of cylinders 12 inches in 
diameter, and providing a tube for each, one case alone 
being provided for the whole." 
t u i) e, w i t h Such a tube, with branches radiating from a single point, 

branches. ' & & h *. ' 

has been devised by Captain Steward. In the head of each*, 
branch he places a small priming charge, and the gas pro : 
duced by its ignition would no doubt act in a similar way, 
down each branch, to that of the fuse with the single tube. 
The advantages of a single fuse, or center of ignition, in 
each charge are very great. It is extremely difficult to test 
a number of fuses of high electrical resistance in a single 
circuit without a very delicate galvanometer, or such an 
increase of power in the testing-battery as to run the chance 
of firing one of the fuses, and thus causing a premature ex- 
plosion. Again, one bad fuse, among a number combined 
for the ignition of a large charge, might destroy the effi - 
ciency of the whole arrangement, or cause difficulties in igni- 
tion. And finally, should the tests indicate something wrong, 
it would be a comparatively easy matter to replace a single 
defective fuse at one center of ignition ; whereas the re- 
adjustment of a number would involve considerable difficul- 
ty, and probably necessitate the emptying out of the entire 
case. 

A few experiments on a very small scale, with charges o 1 " 
6 pounds of powder, were tried by the floating obstruction 
committee to ascertain the value of the tube, but no definite 
results were obtained, nor is it likely that they would be 
with such small charges, supposing that the theory that a 
charge of 250 pounds of powder may be fired with a single 

center of ignition is correct. In order to settle this question 
it would be necessary to try comparative experiments with 
charges of not less than 500 pounds of powder, the com- 
parative effects with and without the tube being carefully 

measured by any suitable means. 

Though, for the present, we are not prepared to concur in 

Captain Steward's ideas, that India-rubber bags, combined 
with tubes, but without a metal covering of such strength 



113 

as to develop the explosive force, are sufficient practically 
to secure complete ignition of a charge ; or that a considera- 
bly elongated cylinder is the best form of case j still the 
tube arrangement is extremely ingenious, and would proba- 
bly render the use of a large number of fuses in a charge 
of powder of considerable bulk unnecessary. 

Several other methods have been suggested for producing Austrian pi au of 

■*- ° surrounding fuse 

this very desirable result of a thorough ignition of the charge ; with gun-cotton. 
for instance, the Austrians place a pound or two of gun-cot- 
ton in actual contact with the fuse, and this substance be- 
ing much quicker of ignition than gunpowder, the gas and 
flame produced is supposed to permeate the interstices be- 
tween the grains of the latter and thus secure a thorough 
combustion of the charge. 
Lieutenant Chadwick, E. E., has suggested enveloping Gun-cotton bag 

7 7 Gi=> ^« ° suggested by Lieu - 

the charge of powder in a bag of gun-cotton, under the sup- te » ant cimAwfek,. 
position that by su rroundiug it, as it were, by an envelope 
of flame, which would be produced by the, more rapid igni- 
tion of the gun-cotton, the combustion would be con turned 
inward and that none of the powder could escape un burnt. 
The effect of such an arrangement would be well worth try- 
ing. 

In order to prevent any chance of a miss fire, the Aus- eaS^cStefSTiJ! 
trians recommend the use of two fuses at each center of ig- nition - 
nition, so that if one fails there is a chance for the other to 
produce the required result, and there is no doubt that in 
all cases, especially where there is any question as to the 
good quality of the fuses, this is a very necessary precau- 
tion, especially when there is only one center of ignition in 
a charge. It must not, however, be confounded with the 
use of two fuses, one at each of two distinct centers of igni- 
tion, in a charge; it is simply the arrangement of two fuses 
at a single point where one, if good, would do the work, and 
is only a matter of precaution. 

When no arrangement, such as Steward's tube, is used, F . i:cin ^ fuses iu 

07 7 7 position. 

and we wish to distribute a number of fuses about in the 
mass of any given charge, a very good means of keeping 
them in their proper position is to lash them to nieces of 
wood which, being rigid, may be arranged so as to remain 
stationary. This should be done before the charge of pow- 
der or other explosive is put in the case. 
With reference to the above remarks on the subject of a strong case re- 

quired for gun 

the number of fuses required and their distribution in a powder tired with 

n i . , . ordinary fuse. 

given charge 01 large size, it must always be borne in mind 
that when gunpowder or gun-cotton fired with an ordinary 
fuse is used, a case of sufficient strength to develop the 
8 



114 

force of the charge is always necessary, whatever number 
of points of ignition may be employed. In fact, it cannot be 
too strongly impressed that the provision of a strong case 
(except where gun-cotton, fired with a detonating fuse, or 
some compound similar in the character of its ignition, is 
used) is a matter of vital importance. When gun-cotton 
fired with a detonating fuse is used, the strength of the 
case, as regards the development of the explosive force of 
the charge, seems to be a matter of no importance ; it is to 
be hoped, therefore, that we may be able to adopt this ma- 
terial and mode of ignition, which would eliminate one con- 
siderable source of difficulty. 



CHAPTER VII. 

ELECTRIC CABLES. 

The next point to be considered is the most suitable form 
of insulated conducting- wire or cable for employment with 
electrical submarine mines. 

The qualifications required in such a conductor are as el Q^ fi c ^ b t gJ 1S0f 
follows : 

1. Capacity to bear a certain amount of strain without 
breaking. 

2. Good insulation, composed of such a substance that it 
may be readily stored and kept for a considerable time with- 
out being injured. This is. an essential, as the lines will 
only be submerged while actually in use in time of war, for 
which purpose they must consequently be kept in store, 
and always ready in sufficient quantities. 

3. For situations where there is a rocky or shingly bot- 
tom they must be provided with an external covering capa- 
ble of protecting the insulation from destruction. Special 
precautions must, of course, be taken to secure the cables 
at points where they may be necessarily exposed to a con- 
siderable wash of the sea, such as the places where they 
may be led into a fort, &c. ; but as there are others where 
no such special precautious can be applied, we must provide 
for the contingency by an external protecting covering over 
the insulation. 

4. Pliability, so that it may be wound on or jjaid out from 
a moderately-sized drum without injury. 

Several forms of cable have been devised to meet the Austrian cables 
above conditions. That used by the Austrians was manu- mines. 
factored by Messrs. Siemens Brothers, of Charlton, and con- 
sists of a metallic conducting-wire, insulated with gutta- 
percha, and protected externally by hemp and by several 
plies of copper tape, wound on in a peculiar manner, so that 
each strip overlaps the preceding one, as shown in Fig. 43 ; 
this is a patent of the above-mentioned firm. 

One defect of gutta-percha insulation is its liability to 
become hard and brittle when exposed to dry heat, and the 
consequent necessity of keeping it stored under water. In 
order to obviate this defect, Messrs. Siemens have recently 
replaced the gutta-percha by vulcanized India-rubber in 
some of their cables. 



116 

The following list gives the dimensions and composition 
of some of the forms of cable manufactured by them for mili- 
tary purposes : 



cS 

o 
o 

S 

ft 


Price per statute mile, 
free, on board, in 
London, including 
package. 


cS 

CO 

2 a 

o 

H 


Description. 


3006 

3029 

3030 
3031 
5014 
5015 


£ s.d. 
85 

81 

81 
70 
63 
63 


cwt. 
6 

4i 

si 

Si 


A conductor, consisting of a strand of three soft iron -wires, 
each of 0.05 inch diameter, insulated with two layers of 
gutta-percha and compound to 0.236 inch, sewed with 
best Italian hemp strings, and covered with one contin- 
uous copper sheathing to a total diameter of 0.39 inch. 

A conductor, strand of three soft iron wires, each 0.03 inch, 
covered with three layers of vulcanized India rubber to 
0.264 inch, a layer of hemp, sheathed with copper sheet, 
and covered with tape painted white. 

Same as last, but covered with plaited hemp instead of 
painted tape. 

Same as 3029, but no outer covering of tape or hemp on the 
"copper. 

Same conductor as 3029, sewed with hemp, and covered 
with tape painted white, with no copper sheathing. 

Same as last, but covered with plaited hemp instead of 
painted tape. 

• 



d fe^^f se abi°H ^ e nave occasionally found the copper-tape covering on 
protected with these cables to act prejudicially under certain circumstances, 

copper tape. L " 

as, for example, if by any chance a kink occurs in paying 
out the line, and a sharp strain is suddenly applied, the cop- 
per tape is at that point drawn in such a way as to cut through 
and destroy the insulation. In handling these cables, there- 
fore, it is necessary to be extremely careful. When once 
laid down this outer covering of copper tape appears to be 
a very efficient protection, and it is, of course, less affected 
by the sea-water than iron. In using it, however, it is neces- 
sary to take certain precautions to obviate the electrical 
action which would ensue were the copper covering to be 
brought into contact with iron in salt-water. Under such 
conditions the iron would inevitably corrode very rapidly. 
The rapidity with which this electrical action destroys iron 
under the above circumstances is almost inconceivable, and 
much trouble on this account has been experienced in car- 
rying on some of our experiments. 

An elevation and section, showing the general construc- 
tion of Messrs. Siemens's cables in full size, are given in Fig. 
43 ; (a) is the conductor; (b) the insulation of gutta-percha or 



117 



Indian rubber ; (c) and (d) two coverings of hemp ; and (e) the 
outer protecting copper sheathing, laid on in a peculiar way. 

Another form of electric cable, suitable for submarine min- Hooper's cable. 
iug purposes, is manufactured by Mr. Hooper, of the Tele- 
graph Works, Mitcham, (now Hooper's 
Cable Company, limited,) and possesses 
many qualities which render it espe- 
cially applicable for this service. It 
may be described as follows : 

A metal conducting- wire, generally 
of copper, covered with an alloy to 
protect it from chemical action ; over 
this is a thin coating of raw India rub- 
ber, then a thin coating called the sep- 
aration of India rubber, mixed with 
oxide of zinc ; over this is a thickness • 

of vulcanized India rubber, more or 
less, according to the amount of insula- 
tion and protecting covering required, 
and the outside protected by tarred 
hemp and iron wire, or, where the cable 
is not to be subjected to such usage as 
to render an outer wire cohering neces- 
sary, by a simple layer of India-rubber 
felt. In the process of manufacture, 
the India-rubber, after being laid on, 
is subjected to a very high temperature, 
under a pressure of steam at 300 degrees 
Fahrenheit, which fuses it into a solid 
mass; and while thus improving the 
insulation, renders it indestructible by 
heat of any degree likely to occur even 
in a tropical climate. 

The object of the separator is to pre- 
vent the sulphur of the outer or main insulator penetrating 
to, and attacking, the metal conductor. 

The high degree of insulation attained is due to the use 
of India rubber, which is an excellent dielectric, and its 
capabilities in resisting high temperatures have been very 
severely tested in the existing lines in Ceylon, India, 
and the Persian Gulf, most favorable reports of which have 
been received. The advantages claimed for this cable by 
Mr. Hooper are summed up briefly as follows : high insula- 
tion, flexibility, and capability of withstanding dry atmo- 
spheric heat, which would destroy gutta-percha. 





118 







&3 



A full-size elevation and section showing the general con- 
struction of Hooper 7 s cables are given in Fig. 44; (a) is the 
conductor ; (b) the India-rubber insula- 
tion ; (c) the covering of tarred hemp : 
and (d) an outer covering of iron wires ; 
No. 11, B. W. G., each separately cov- 
ered with tarred hemp, wound on spi- 
rally. 

The table in page 120 gives in a com- 
prehensive form the different cables 
of Hooper's form, suitable for subma- 
rine mining purposes. Those with a 
stand conductor of three or four small 
wires only, viz: Nos. 323 A, 321 A, 376 
and 323, do not possess a very large 
« amount of tensile strength, which, being 

necessary for submarine mining pur- 
poses, must be supplied by the addition 
of an outer covering as already de- 
scribed. 
Defect of in- Iudia rubber insulation possesses one 

dia rubber insu- 
lation, defect as compared with gutta-percha, 

viz, that it does not cling, as it were, 

to the metallic conductor ; and that, 

consequently, if the India rubber is once 

cut through, any strain in .the cable has 

a tendency to pull the conductor away 

and increase the fault. The conductor 

cannot be thus pulled away from the 

insulation, when the latter is formed of U 

gutta-perch, which seems to cling to it H 

As far as we yet know, how- 
ever, India rubber is not so easily affected by dry heat as 
gutta-percha, and is therefore preferable for storage ; the 
latter cracks and perishes unless considerable care is exer- 
cised in preserving it, which is best done by keeping it 
under water. India rubber possesses higher dielectric pro- 
perties than gutta-percha. 

A cable, very similar in appearance to Hooper's, is man- 
ufactured by the India rubber, Gutta-percha, and Tefegraph- 
works Company, of Silvertown, North Woolwich. The chief 
difference in this cable, as compared with Hooper's, appears 
to be the absence of the separator, on the use of which, 
however, Mr. Hooper lays peculiar stress. The form of 
insulation adopted by the Silvertown Company is called 
Gray's patent. 



Cx 



Advantages of an d prevent such a result. 

India rubber in- 
sulation. 



Grav's cable. 



119 

A cable of this form was used in the operations against „ Cal ?J e . used , in 

° deino ltion of the 

the wreck of the Golden Fleece at Cardiff in December, ™-eck "Golden 

7 Fleece." 

1869, and January, 1870. 

It consists of a strand of 3 No. 20, B. W. G. copper wires, 
insulated with India rubber (Gray's patent) to a diameter 
of t 2 q inch, and protected externally with two servings of 
tarred hemp, wound spirally in opposite directions. This 
cable possesses considerable tensile strength ; when one 
end of a short length was made fast to a rigid point, 
it resisted two men pulling at it with their full strength 
without injury. It remained perfect during the whole of 
the operations against the wreck of the Golden Fleece, 
which extended over a period of two mouths of very 
rough usage, and turned out to be admirably suited for 
the purpose to which it was applied. Its cost is about 
£35 per mile. 

For rocky bottoms or situations where the cable is sub- 
jected to risk of mechanical injury, a further external pro- 
tection of iron wires and tarred hemp must be used. This 
would of course increase the cost. 

A full-size elevation and section of this cable, which give 
a very good general idea of the forms manufactured by the 
Silvertown Company, are shown in Fig. 45 ; (a) is the 

Fig. 45. 




metallic conductor; (b) the insulating material, (Gray's 
patent;) (c) and (d) two servings of tarred hemp, wound 
spirally in opposite directions. 

A multiple cable may in many cases be found convenient 
where it is required to carry a large number of wires in a 
compact form into a fort. The following description of 
cable has been designed for this purpose, and seems to meet 
the necessities of the case : 

It is composed of seven distinct cores, each of which consists 
of a strand of 3 No. 22, B. W. G. copper wires insulated 
with India rubber (Gray's patent) to a diameter of -f^ inch. 
The interstices between the cables are filled with hemp fibers 
disposed longitudinally, to afford as much tensile strength 
as possible, and the whole is protected with a double serving 
of tarred hemp. The cost of this cable will be- about £220 
per mile. For a rocky bottom, a situation where the cable 



Multiple cables 



120 























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121 



is liable to injury, a further external covering of iron wires 
and tarred hemp, laid on as is usual for the protection of 
submarine cables, becomes necessary ; this addition would 
increase its cost. 

A full-size elevation and section of this cable are shown 
in Fig. 46 ; (a, a, a) are the conductors of the several in- 
sulated wires of which it is com- 
posed ; (b. b, b) the insulation of 
the same; (c) hemp fibers dis- 
posed longitudinally between the 
insulated wires to give tensile 
strength; (d) and (e) two serv- 
ings of tarred hemp wound on, 
the first in one direction and the 
second in another. 

Seven conductors are used in 
this cable, because when all 
of the same size, the six outer 
wires fit compactly round a single 
one in the center. Seven is there- 
fore a*convenient number to com- 
bine in any multiple cable. When 
more than seven conductors are 
required, the diameter of the in- 
sulation of the center one must 
be increased to give room for the 
others to fit round it. 

It must be borne in mind that Defects of mui- 

ipie cables. 

when a multiple cable is used, 
any attempt to fire a mine in con- 
nection with it by friction al elec- 
tricity would be nearly certain 
to result in the explosion, by in- 
duction, of every other mine at- 
tached to the same cable. 
Experiments have proved that ^. In . duct 1 i0 " wlu . n 

- 1 - *■ fnetionalelecf na- 

if several lines of insulated con. ty is used. 

ducting cable are laid in the same 
trench for a few hundred yards, 
the inductive effect of the electri- 
cal charge, generated by a field-pattern Austrian Motional- 
machine, is so great that its discharge, through one cable so 
placed, is sufficient, not only to fire the fuse in immediate con- 
nection with it, but also, by induction, to ignite every fuse in 
connection with every other cable in the same trench. This 
effect occurs equally when the cables are as much as three 




122 

feet apart, provided they lie parallel to each other for a 
few hundred yards, and whether the shore-ends of the 
cables, the fuse in connection with which are not intended 
to be fired, are insulated or put directly to earth, the con- 
nections beyond the fuse being to earth, or even when the 
latter are insulated, provided a very few yards of conduct- 
or exist beyond the fuse. Such a length as must necessa- 
rily be used between a charge and circuit-closer would be 
quite sufficient to insure ignition by induction in this way. 
The current rushes in, as it were, through the fuse, to charge 
the small length of wire existing beyond it, and determines 
its ignition. 
Result of ex- The following record of some experiments, tried with a 

periments on in- .... „ 

duction. view or ascertaining this inductive effect, gives a very good 

idea of the danger of using frictional electric^- under such 
conditions : . 

Two Cables, each consisting of a strand of 7 No. 22 copper 
wires,' insulated with Hooper's dielectric to a diameter of 
i 3 o inch, were laid side by side on dry ground, for a distance 
• of half a mile, the extremities, to which the fuses were to 

be attached, being separated by a distance of 20 yards. When 
fuses were fired directly through No. 1 conductor, by a field- 
pattern Austrian ebonite frictional-machine, fuses were fired 
bj 7- induction on No. 2 line under the followiug conditions : 

1. With both ends of No. 2 cable to earth, viz, that at 
the firing station, and that beyond the fuse. 

2. With the end of No. 2 cable at the firing station insu- 
lated, and the connection beyond the fuse to earth. 

3. With the end of No. 2 cable at the firing station to 
earth, and an Abel's fuse to represent a considerable elec- 
trical resistance at this point, introduced between the cable 
and earth-plate, the connection beyond the fuse being, as 
before, to earth. In this case both the fuses, one at each 
end of No. 2 cable, were fired. 

The same results were obtained under the three several 
conditions specified, when two fuses, in continuous circuit, 
were introduced on No. 2 cable, instead of one; and again, 
when three fuses were substituted, in continuous circuit. 
These last experiments were tried in order to ascertain 
whether the introduction of a considerable electrical resist- 
ance into the circuit would overcome the effect of the in- 
duced current; with two fuses the electrical resistance of 
the whole circuit would be nearly doubled, and with three 
nearly trebled, the comparative resistance of the conduct- 
ing cable being insignificant. 

The cables were subsequently arranged three feet apart 



123 

for half a mile, and the experiments, under the three con- 
ditions enumerated, repeated, one fuse only being introduced 
at the distant end of No. 2 cable, and one between the same 
cable and earth connection at the firing station; with these 
arrangements both the fuses on No. 2 cable were fired by 
induction, as before, on every occasion. 

Again, a fuse was introduced on No. 2 cable, with three 
yards of insulated cable beyond it, the end of this short 
length being insulated, the cables being, as before, three 
feet apart. Under these conditions the fuse was fired with 
the same certainty as in the first experiment. 

The object of this last experiment was to ascertain the 
effect of the induced current on a fuse with a circuit-closer 
beyond it, the connection with the circuit-closer being rep- 
resented by the three yards of cable, insulated at its outer 
extremity. 

A constant battery of 100 cells, of DanielFs form, was Experiments to. 

induction with 

next employed as the firing agent in connection with No. 1 constant battery. 
cable; but no fuse was fired by induction on No. 2 cable 
under any of the conditions enumerated. 

We may therefore assume that such a battery might be 
used with safety to fire any given mine of a system, when 
the conducting cables lie in close proximity and parallel to 
each other for a considerable distance, or when a multiple 
cable is used. 

The fuses used were the newest and most sensitive form 
of Abel's, and the experiments, while establishing, beyond 
a doubt, the powerful inductive effect of a discharge of 
frictional electricity, gave substantial proof of the great 
delicacy of these very sensitive fuses, and of their good 
qualities as simple agents of electrical ignition, while at the 
same time rendering it very evident that the utmost care 
is indispensable in testing and using them. 

The inductive effect with a multiple cable would mani- 
festly be very much increased in consequence of the prox- 
imity of the adjacent conductors. Frictional electricity 
must not, therefore, be used to fire charges in connection • 
with a multiple cable, or even when separate cables lie 
parallel to each other for a short distance, in connection 
with any system of submarine mines. 

Induction does not occur to such an extent as to fire an 
Abel's fuse, when a constant battery is employed. Such 
a battery may therefore be used with perfect safety to fire 
any particular mine of a system attached to a multiple cable 
without endangering the others. With the platinum fuse 
there is no danger whatever of ignition by induction. 



124 

connSn b o°fiines * n or & er to facilitate the connections of the several sepa- 
to multiple cable. ra te lines, diverging from the extremity of a multiple cable, 
a testing-box has been designed. Into one side of this box 
the multiple cable is introduced through a water-tight joint, 
while the separate cables make their exit on the other side, 
through similar joints, and pass thence to the several mines 
of the system. Within the box is provided an additional 
separate water-tight joint for each cable, so arranged, on a 
principle designed by Quartermaster-Sergeant J. Mathieson, 
E. E., that each cable may be rapidly connected or discon- 
nected to give facilities for examination and testing. In 
order to bring this box to the surface for the latter purposes 
it is only necessary to provide a buoy and a line of sufficient 
strength to enable it to be weighed. The buoy-line must be 
strong enough, not only to carry the weight of the testing- 
box, but also that of a short length of the cables connected 
with it, sufficient to reach to the surface. This testing-box 
must be placed in such a situation as to be easily attainable, 
even in presence of an enemy's blockading squadron, and 
the buoy attached to it must not be conspicuous. It i s 
essential that it should be in a safe and well-guarded position, 
as any injury to it, or to the multiple cable, would be fatal 
to every mine connected with it. The necessity for safety 
would also regulate the length of the multiple cable and the 
point at which the separate cables should diverge; this 
must always be dependent on local circumstances. A detailed 
description of this testing-box shall be given hereafter. 
„ ,_, . iT . Another form of cable has been suggested by Quarter- 

Cables with . 00 d ^ 

branches designed mas ter-Ser2feant J. Mathieson, R. E., in connection with a 

by Quarter in as- ^ ' 

Ter-sergeant Ma- system of electrical self-acting mines, arranged to be fired on 
the circuit being closed by the contact of a ship, the igniting 
agents being a quantity battery and platinum fuse. The 
following is a description of his proposal: From his firing 
station he carries a multiple cable, (a,) Fig. 47, to a test-box, 
(&,) from this test-box, which is arranged in a precisely 
similar manner to that already described ; single conducting 
cables (c, c, c,) (insulated at their outer extremities,) with 
branches, (d, d, d y ) are carried to the positions in which it is 
required to place the mines; finally, to the branches are 
connected the several mines with their respective circuit- 
Closers, and when any one of these latter is struck by a 
vessel, the circuit of a battery, in connection through the 
multiple cable (a) with the particular line (c) to which it is 
attached, is closed and the mine fired. After any particular 
mine has thus been fired it becomes necessary to cut it out 
of the circuit, otherwise the current passing away through 



125 



tbe bare extremity of the fractured wire, to which it had 
been attached, would cause such a loss of battery power as 
probably to prevent any fuse iu connection with the same 
cable being fired, even if its circuit-closer were struck by a 

Fie. 47. 




vessel. Furthermore, it is necessary to eliminate this ex- 
pended line from the system without going near \t. In order 
to do this Quartermaster Sergeant Mathieson proposes to 
use a quantity battery, (Grove's or Walker's,) and to place 
a short length of thin platinum wire at a point (e) in the 
branch (d)' between the main cable (c) and the platinum 
fuse (/,) which latter fires the charge. The platinum wire 
at (e) is so arranged, within a Mathieson's connector or 
other suitable insulated covering, that on its being fused 
the extremity of the cable at (e) is at once insulated, under 
which circumstances the loss of current, through the fractured 
extremity of the cable of an exploded mine, would be stopped 
and the full force of the battery be preserved to fire any 
mine attached to the same cable, (c,) which might be subse- 
quently struck by a passing vessel. It is easily understood 
how two short lengths of thin platinum wire at (e) and (/,) 
in the same continuous circuit, may be fused simultaneously, 
and thus the charge would be exploded and the ruptured 
conductor cut off (insulated) at the same moment by the 
current of the same battery. It may also be easily under- 
stood how an arrangement might be made, within the test- 
box (b) by which a whole cable, as (c) might thus be cut 
off, by simply fusing a short length of platinum wire in 
connection with it,- should such be considered necessary. 

In order to prevent any chance of failure from the fusion 
of the platinum at (e) before that in the charge at (/,) ad van- 



126 

tage is taken of the fact that if two lengths of platinum 
wire are placed in simple continuous circuit, one being 
slightly longer than the other, the longest will be fused first. 
The battery power to fuse any given length of platinum 
wire in circuit, as at (e) and (/,) is easily calculable, and, as a 
matter of precaution, a considerable excess over the calcu- 
lated number of cells (say double) should be used in prac- 
tice, to prevent the smallest chance of failure. It must 
always be remembered that calculations are made under the 
supposition that the batteries are perfect, insulation abso 
lutely faultless, and fuses, &c, of uniform resistance ; con- 
ditions which never really exist in practice, however good 
the arrangements may be, and which a very small defect 
may seriously disorganize. 

Experiments have proved that the combinations described 
are not only quite practicable, but capable of being arranged 
to act effectively without any considerable amount of 
complication. 
wan proposed This plan has been proposed as a substitute for the 
TOeci^caimrnS mechanical self-acting system. It must still undergo a fur- 
ther trial, and, if successful, will enable us to get rid of 
that element of equal danger to friend and foe which is in- 
separable from any purely mechanical method. It is easily 
seen that by it perfect safety is secured to a friendly ves- 
sel by simply detaching the firing battery. 
cable suitable ^ Qe caD le proposed consists of a strand of 7 No. 20, B. W. 
for tins purpose, q. copper wires, insulated with India rubber, (Gray's patent,) 
to a diameter of T 3 o 2 ¥ 4 o inch, and protected with a double 
serving of tarred hemp. The branches formed of the same 
core are one yard long each, and inserted at any suitable 
intervals on the main cable, and are similarly protected with 
tarred hemp. 

A further external protection of iron wires and tarred hemp 
must be added to this cable for situations where such may 
be required. The cost of such a cable is about £120 per 
mile, or, with the additional external covering, somewhat 
more. 

Experiments are about to be undertaken with it in order 
to test its efficiency. 

A full-size elevation and section of the form of cable, suit- 
able for this arrangement, are shown in Fig. 48; (a) is the 
main metallic conductor; (a 1 ) a branch conductor; (b) the insu- 
lation, (Gray's patent;) (c) and (d) servings of tarred hemp, 
wound on, the first, (c,) in one direction, the second, (d,) in the 
other. 



127 




Some further experience is re- Beat form oi 

cable for general 

service. 



Gray" 



quired in order to determine defi- 
nitely the peculiar advantages 
and defects of these several cables, 
but with our present knowledge, 
and taking all the conditions to 
be fulfilled into consideration, 
Hooper's core, or something simi- 
lar to it, would seem to be the 
best form at present manufac- 
tured, which would be capable of 
being used for submarine mines, 
combining, as it does, high insu- 
lating power with a capability to 
resist injury to the insulating 
substance, (vulcanized India rub- 
ber being one of its principal com- 
ponents,) and a considerable 
amount of flexibility. For rocky Hooper 
or shingly bottoms, where there is 
much rubbing on the surface of 
the cable, Mr. Hooper proposes to 
protect it by an outer covering 
of iron wires, each covered with 
hemp, laid on in the manner 
shown jm Fig. 44. It would not 
be difficult to lay on such a cov- 
ering anywhere, at a foreign sta- 
tion, for example, or to repair it 
when required. Without some external covering Hooper's 
core does not possess very high tensile strength and must 
be used carefully. 

Gray's patent insulation is, very similar to Hooper's in 
many of its characteristics, and his external covering of 
tarred hemp, laid on first in one direction and then in 
the other with rather a long twist, adds considerably to the 
tensile strength. 

One mode of protecting an insulated cable, suggested by 
the floating obstruction committee, and almost simultane- Jjj£ f °* 2S33 
ously by Captain David, R. M. L. I., while the latter was cables 
under instruction in the electrical school at Chatham, is to 
cover it with rope, to place it in the core, as it were, of a 
hempen cable. Two short lengths of Hooper's core have 
been covered in this manner, in the rope manufactory at 
Chatham dock-yard, for trial. The insulated wire was held 
steady in the center, and the rope was made upon it in the 




Outer protec- 



128. 

usual way, so that in outward appearance it differed in no 
respect from an ordinary hempen cable. It has been sug- 
gested by the floating obstruction committee as a cheap and 
ready means of covering an electrical cable, and so pro- 
tecting it from external injury, and from experiments tried 
with the lengths in our possession, it promises to be very 
useful in certain positions, and might no doubt be used with 
advantage when the more approved form of cable is not 
obtainable, and when the bottom on which it is laid is not 
too shingly or rocky and likely to cut through the external 
hempen coverings. In forming the rope upon it, considerable 
care is necessary to prevent any great amount of tension 
or torsion coming on the insulated wire, as either one or the 
other is likely to injure it. 

It was suggested by Captain David, in connection with 
an idea he had for exploding charges in combination with a 
floating boom, or to indicate that a boom was broken. 
captain David's His idea was to lay one or more of such rope protected 

au electric cable electric cables along the whole length of the boom, carefully 
attaching them thereto. With such an arrangement any 
attempt to break the boom must be accompanied by a frac- 
ture of one of these cables ; and the bare extremity of the 
conducting wire, falling into the water as soon as the cable 
was cut through, would be sufficient to complete the circuit 
of a battery, one pole of which was attached to the cable 
with the other to earth. It is easily seen how a charge pre- 
viously placed in such a circuit would thus be fired, and 
would destroy any vessel or boat in its vicinity. It would 
only be necessary to insulate the extremity of the cable 
beyond the charge, as regards the firing battery, to render 
the system inactive till the cable was cut. It is, no doubt, 
probable that this cable, resembling in outward appearance 
an ordinary rope, would not excite suspicion and would be 
likely to be cut, but any mine in connection with it, near 
enough to injure a vessel or boat, would also generally be 
near enough to damage the boom itself, a result which would 
not be at all desirable. Some experiments were tried by 
Captain David which demonstrated the practicability of 
the idea, as far as the firing of a charge is concerned, 
such a combi- As an indicator of the continuity or otherwise of a boom 

iSrtor.f ulasan at night or in a fog, it would probably be useful. The .ar- 
rangement of an insulated cable for such a purpose would 
be the same as that for firing a mine, but instead of a charge of 
powder or gun-cotton, a galvanometer would be introduced 
into the circuit, and a fracture of the conductor indicating 
the breakage of the boom by storm or an enemy's operations, 



129 

would at once be indicated by a deflection of that galvan- 
ometer, consequent upon the current from the battery, the 
circuit of which would be completed through the severed 
cable as before. In this manner a most effective watch 
from the interior of a fort Could be kept over obstructions 
in a channel, even though such obstructions were perfectly 
invisible from any cause whatever. 

The electrical conducting cable is perhaps the most im- improvised dec 
portant item in any system of electrical submarine mines - tllccable8 - 
an accident to it would nearly always render a mine inef- 
fective ; it is therefore a difficult matter to treat of, in refer- 
ence to any improvised arrangements that may be practica- 
ble. As a general rule, in the event of the more approved 
forms of cable not being obtainable, the test conducting- 
wire and insulator at hand should be used ; and, bearing in 
mind the conditions to be fulfilled, already enumerated, it 
should be most carefully tested under a considerable press- 
ure of water before being employed. Any of *he ordinary 
forms of conducting- wire insulated with gutta-percha, might, 
with the addition of some external protecting covering, be 
made available, or even a wire insulated with a thick cover- 
ing of well- tarred canvass might answer for a short distance. 
In forming an impromptu cable, a large conducting- wire of 
small electrical resistance should be selected. The reason 
of such a selection is manifest, with reference to the well- 
known law of division of electrical currents. 
9 



CHAPTER VIII. 

WATER-TIOHT AND INSULATED JOINTS AND CONNECTIONS. 

The next point to be considered is the mode of carrying 
the conducting- wires and attached fuse into the charge, so 
as to insure a water-tight joint, and keep the arrangement 
in proper condition for ignition at any moment required. 

The great object is to exclude the water ; this was effected 
in the Austrian apparatus by means of a stuffing-box. 

Mat hie son's The following suggestion of Quartermaster-Sergeant J. 
dicing fuse'Tnto Mathieson, R. E., is perhaps the best that has yet been de- 
vised for attaining the above very desirable object, and it not 
only possesses the advantage of being extremely water-tight, 
but is also capable of being opened at any time, with the 
greatest facility, for the examination of the fuse. The mode 
in which this may be done may be easily understood from 
the following descriptions : 

objects to be at- He has designed several arrangements to meet the objects 
to be attained, which may be enumerated as follows, viz 7 
that the opening, through which the conducting- wires of 
the fuse are introduced, may be water-tight, and that the 
apparatus may be easily unscrewed and the fuse taken out 
for examination , or for the introduction of a new one, in the 
event of a defect being discovered. 

Apparatus for a One of these is shown in section in Fig. 49 ; (a a) are two 
cylinders of ebonite, through which a pair of holes are bored 
for the reception of the wires attached to the terminals of 
an AbePs fuse, and with shoulders (b b) on each, the lower 
one arranged to fit on a flange, attached to the metal case, 
to contain the charge, and the upper to receive a metal 
screw (c c) which, when screwed home, would exercise a 
pressure tending to force the two ebonite cylinders into close 
contact, as well as to fix them firmly into the case for the 
charge. Within the holes for the reception of the insulated 
conducting- wires (//) are a pair of ebonite tubes fitting- 
over the latter, and their extremities beveled into a wedge 
form. Four cylinders of vulcanized India rubber, (g g,gg,) 
each perforated to enable them to pass over the insu- 
lated wires, (/ /,) are placed just over the wedge-formed 
extremities of two ebonite tubes (e e.) A ring or washer 
(h) of vulcanized India rubber is placed between the shoulders 
of the lower ebonite cylinder and the flange of the metal 
case on which it rests. A metal shoulder, (i,) formed with a 



metal case. 



131 



female screw to correspond with the screw (c c,) receives the 
latter, and it is easily seen how, when (c c) it is screwed 




home, the several parts of the apparatus are forced closely 
together, and pressure is brought fco bear upon the India- 
rubber cylinders (g g, g g) and the India rubber ring or 
washer (h.) These are thereby forced into all the interstices 
in their vicinity, and everything becomes perfectly water- 
tight. The shoulder [i i) should be cast or welded on to 
the case to contain the charge, so as to form one solid piece 
with it. When the metal, of which the case for the charge 
is composed, is iron, the screw (c c) must also be of iron ; 
if any other metal, brass for example, were used in contact 
with iron in sea-water, an electrical action would be imme- 
diately set up, and the iron would be very rapidly decora- 



132 



Apparatus for 
use with a barrel. 



posed. This is an important point to remember in the 
construction of apparatus of this nature. 

Another similar form of apparatus has been designed by 
Quartermaster- Sergeant Mathieson, E. E., for carrying the 
conducting- wires into a charge placed in an ordinary wooden 
barrel; this is shown in section in Fig. 50, and is precisely 




similar in principle to that for the metal case, Fig. 49. There 
being no iron here to decompose, the metal screws, &c, may 
be formed of brass, which is an advantage, as this latter 
metal is more easily worked in the form required ; (a a) are 
the two ebonite cylinders ; (b) the brass coupling-screw; (c) 
a brass socket, in connection with another brass screw (d) 
within the barrel ; (e e) are the ebonite tubes as before ; (//) 



133 

India-rubber washers, and (g g) the insulated conducting- 
wires to connect the fuse. The screw (d) is furnished with 
spikes, which grip the inside of the barrel and secure rigid- 
ity. 

Another form of apparatus, somewhat similar to that Apparatus tor 
described in page 96, but an improvement thereon, has been wSefuse^ a 
designed for use with a platinum-wire fuse and a metal 
case for the charge ; this is shown in section, Fig. 51 ; (a a) 




is a shoulder of peculiar form, cast or welded on, and form- 
ing one solid piece with the metal of the case, in which a 
circular opening, 4 inches in diameter, is left for the intro- 
duction of the charge of gun-cotton disks; (b b) is a socket 
with shoulder, made to fit over (a a-,) (c c) is a metal coup- 
ling screw; {(1) is the platinum-wire f use, formed on precisely 
similar principles to that described in page 96, but in this 
case made to screw into the socket (b b) so that it may be 
taken out for examination without disturbing the main 
arrangements by which the loading-hole is secured; (e e) 



134 



are vulcanized India-rubber rings or washers, by which the 
whole is made water-tight, in precisely a similar manner to 
that already described ; (//) are the fuse terminals ; these 
are insulated with vulcanite, which has been made to adhere 
to the ebonite frame (g) of the fuse, the cavity (d) being 
filled in with a composition consisting of 16 of pitch, 2 of 
bees-wax, 2 of tallow, and 6 of gutta-percha, pressed into it 
in a melted state. When cool this composition becomes 
quite hard, and completely insulates the fuse terminals 
within the ebonite frame. This composition has also been 
found very effective in preventing water passing clown along 
the conducting- wires, between them and the insulation, 
(when the apparatus is submerged to such a depth as to en- 
tail a considerable pressure,) and thus entering the charge. 
The addition of gutta-percha to the water-proof composition 
has the effect of hardening it materially. The thin plati- 
num wire, (h,) forming the fuse, is soldered to the terminals 
in the usual way. 
Temporary wa- In ordinary submarine practice, or when a good form of 
t£n pro ° f connec ' connector is not to be had, the following composition, viz, 
1 tallow, 8 pitch, and 1 bees-wax, will be found very good. 
The vessel or can in which the charge is to be placed, hav- 
ing been formed with a shoulder or neck (see Fig. 52) of 




sufficient size to receive a moderately large bung, the insu- 



135 

lated conducting -wires (a a) having first been attached to 
the fuse (b) are passed through two holes in a bung, (c,) 
which latter is passed into the neck, which it should fit 
tightly, and the above composition is then pressed into the 
space (d) above it. This composition soon becomes hard, 
and renders the whole water-tight. It is amply sufficient 
for all charges to be fired soon after submersion. It becomes 
plastic at about 150° Fahrenheit. 

The addition of a little gutta-percha, as already stated, Much care neces- 
hardens this composition and renders it less likely to be af- ShMg^switifhea? 
fected by atmospheric heat. More care is, however, neces- e compositlori - 
sary in using it, after the gutta-percha has been added, be- 
cause the higher the temperature the nearer it approaches 
to the igniting point of an explosive, and it may be super- 
heated without indicating the fact by any outward appear- 
ance. Gutta-percha becomes plastic at a temperature of 
about 160° Fahrenheit, and should never be used by itself 
to seal up the bungs or connections of loaded cases. Se- 
rious accidents have, on more than one occasion, occurred 
when it has been used for this purpose. When using any 
of the new forms of explosive, which ignite at compara^ 
tively low degrees of heat, or even with gun-cotton, the 
temperature at which the composition used to seal up a 
charge becomes sufficiently plastic is a matter which must 
be most carefully considered. 

An improvement upon this plan is shown in section, Figs. An-ang ement 
53 and 54 ; (a,) Fig. 53, is a tin socket, in the form of a very with clay 1oint 
long truncated cone, with shoulders to support the cork (6) 
through which the insulated terminals (c c) pass to the fuse (d,) 
and with an outside rim or shoulder (e e) to fit into the nozzle, 
(//,) Fig. 54, of the case to contain the charge. The fuse? 
wires, and cork, having been inserted into the socket («,) Fig. 

53, as already described, the top is filled in with water-proof 
composition (16 of pitch, 2 bees-wax, 2 of tallow, and 6 of 
gutta-percha,) shown black in the sections, this is done 
before the fuse is brought near the charge, and there is con- 
sequently no danger incurred from heat. The socket, com- 
plete with fuse, &c, is next inserted in the nozzle, (//,) Fig. 

54, and moist clay (g) is carefully pressed in over it, to fill up 
and keep it steady in its place. A disk of tin, perforated 
in the center, so as just to pass over the top of the socket, 
is then placed over the top of the nozzle (//,) of the case which 
it is made to fit, and its outer and inner rims, at (h h, h h,) are ' 
made water-tight by soldering. During this operation of 
soldering the heat is thus kept well away from the charge, 
and separated from it by the moist clay, &c, so as to be 



136 

perfectly safe. This arrangement was always used, during 
the summer of 1869, in carrying on gun-cotton experiments 
in the Medway, and scarcely an instance, out of a large 
number of charges fired, occurred in which water found its 
way through it. 
Arrangement of One mode in which the charge may be kept dry is to intro- 

fuse in a separate , • . 

compartment. duce the fuse into a small compartment, let m, as it were, 
but totally separate from the charge, as, for example, in Fig. 




55, a tube (a) of tin, made quite water-tight, may be intro- 
duced into the charge, which, however, it should completely 
separate from the priming-powder (&,) in contact with the 
fuse (c,) the remainder of the tube being filled in as before 
with a bung and water-proof composition. The effect of 
firing the fuse in this case is to burst the tin tube {a) by 



137 



means of the priming-powder (6) and thus ignite the mine. 
This may do well enough for small charges, say up to fifty 
or sixty pounds, but for larger masses it is always preferable 
to have the fuse in actual contact with the charge itself. 

The object of this arrangement is to save the main body 
of the charge, in the event of any leakage of water through 
the opening left for the fuse: it was formerly much used in 
submarine explosions, but we are now able to make such 
good water-tight connections that it seems to be almost an 
unnecessary precaution under ordinary circumstances. 

In all cases the fuse or fuses should be carefully tested Fuse must a i- 
electrically, before they are placed in a charge, and this forJ s and* e afte e r 

being placed in 

%. 55. charge - 




testing should be done both singly and in a group, arranged 
in the same combination in which it is proposed to use them 
in the mine itself, and they should be subsequently tested 
after being placed in the charge. 

Next, as regards the best mode of making an insulated 
joint in a cable. Several systems have been recommended 
and have proved perfectly effective. 

For a permanent joint we have the ordinary gutta-percha Permanent joi 
and India-rubber joints, which, under certain circumstances, 
would be very useful for submarine purposes. These are 
somewhat troublesome to make, and would require a con- 



joints. 



in cables. 



138 



siderable time to render them sufficiently good for the pur- 
pose required. They must be made deliberately and are sim- 
ilar to those used for ordinary submarine-telegraph cables. 
The mode of making such insulated joints as recommended by 
the India-rubber, Gutta-percha, and Telegraph- works Com- 
pany, Silvertown, North Woolwich, is as follows : For a gutta- 
permanent gut- percha cable remove about 1J inches of the insulation at the 
ends. After warming gently it is easily pulled off with the 
fingers, (this is much safer than cutting ;) clean the two ends 
with emery-cloth, and file a J-inch scarf on them, (see Fig. 56.) 
The wires are then caught with the scarfs together in two 



ta-percha joint. 



Fig. 56. 




small vises, fixed on a bench, one working on a slide, so that 
they can be set at any required distance apart, and soldered. 
After soldering, clean the scarf off with a small file. Then 
bind it round with four strands of fine copper wire, laid side 
by side j loop one end on the left-hand vise, and wind from 
left to right, taking care that the wires are evenly laid on 
and do not ride over each other ; the length of the binding- 
should be about 1J inches ; the ends of the binding wires 
are now snapped off by a sharp tug with the pincers. This 
binding is then soldered at the center and at the ends, 
leaving tw r o parts of the binding unsoldered, so that if the 
scarf be drawn asunder the four-strand wire shall still connect 
the two ends and form a metallic circuit. 

The joint is then well washed to remove all acid from the 
copper. 
and In scarfing a strand conductor, the two ends are first sol- 
dered, making them solid. If the diameter of the conductor 
exceed No. 14 gauge, two courses of binding are used, the 
first soldered all over, the second in the center and ends 
only. This is the mode adopted for submarine- telegraph 
cables, but for the comparatively short lengths used for sub- 
marine mining purposes, an efficient metallic connection 
may be made, in the case of a strand conductor, by simply 
twisting the wires of the two portions to be joined tightly 
together ; after cleaning them and soldering, care must be 
taken to prevent any projecting ends of wire remaining at 
the junction. 



conductor. 



139 

To complete the insulation, clean the joiut all over with Tocompietem- 
a little spirit of naphtha on a rag, and give it a thin layer of su 
Chatterton's compound ; warm the joint in the flame of a 
spirit-lamp, and taper the gutta-percha by drawing it gently 
with the fingers until it nearly reaches the center ; then with 
a hot tool, designed for the purpose, work the two portions 
together to form a solid mass ; then apply a thin layer of 
coumpound, followed by a strip of sheet gutta-percha J inch 
thick and large enough to cover the whole, warmed together 
with the joint, and lapped round it, taking care that 
the under part and ends shall adhere first ; warm the 
whole gently again, and close it from the bottom upward 
taking care to expel the air in front. When the two edges 
meet, cut them oft' as close as possible with a pair of scissors 
and work them into one another with the tool, doing the same 
at the ends ; then gently warm the whole, and burnish it off 
with the wet hand. In this way the insulation is completed 
to the same diameter as the original. 

In joining gutta-percha the great point to guard against 
is not to give it too much heat ; if it is a litte too hot it be- 
comes oily and will not adhere. 

The insulation having been thus completed, any outer 
protecting covering of wire, hemp, &c, should be laid on 
and secured which completes the operation. 

In the case of an India-rubber cable thefollowing method 
is recommended : 

Before the portions of the conductor are soldered together, permanent la- 
warm the two ends of the India-rubber insulation and iaiu ei J0int ' 
taper them off with a pair of scissors. After the joint is 
soldered and cleaned off in the manner already described a 
little India-rubber solution is rubbed on the small ends of 
the taper of the insulation, and a layer of rubber compound 
tape is wound round spirally and tighly, on the copper core; 
this compound tape is f inch wide; next a layer of India- 
rubber (not compound) f- inch wide is applied, then a thin 
layer of India-rubber solution followed by another layer of 
Indian rubber. Continue the alternate layers of rubber and 
solution until the joint approaches nearly to the diameter 
of the original core, and finish off with one layer J inch wide, 
commencing and finishing 1J inches on each side of the joint. 
These layers must be each laid on very tightly and regularly. 

When required, any outer protecting covering must be 
put on as before. 

In some cases it may become necessary to insulate a gutta- Permanent in- 

u d ° clia-rubber joint 

percha cable with India rubber, and for this purpose the on gutta-percha 
following method is recommended : 



140 

First apply a coating of India-rubber compound, (strip,) 
then warm the gutta-percha and taper it over the compound 
layer, then spread a thin layer of India-rubber solution on 
the gutta-percha ; next apply a layer of India rubber f inch 
wide followed by a thin layer of India-rubber solution. 
Continue the layers until the insulation becomes nearly of 
the same diameter as the original core. Finish off with one 
layer J inch wide, commencing and ending 1J inches on each 
side of the joint. 

In making insulated joints, moisture, grease, and dirt 

hould be scrupulously avoided. So much stress is laid upon 

these points, that the manufacturers of submarine cables 

only employ men with very clean and naturally dry hands 

at such work. 







Temporary 
sulated joints. 



For temporary purposes, that is to say, when a charge is 
to be fired immediately after immersion, it is unnecessary 



141 

to make a permanent joint such as that described. For this 
purpose an ordinary piece of vulcanized India-rubber tubing- 
passed over the naked ends of the conducting-wires from 
extremities of the two cables to be connected, which have 
been previously joined together and, if necessary, soldered, 
answers the purpose very well. 

To prepare this joint, about 1.5 inches of the copper con- tu ^y; ubber 
ductor of each of the insulated wires, which are to be con- 
nected together, are laid bare and thoroughly cleaned. A 
piece of vulcanized India-rubber tubing, (a,) Fig. 57, about 
4 inches in length, is then slipped over one of the insula- 
ted wires. The two clean and bright ends of the wires are 
then spliced or twisted together as shown at (b) Fig. 57, care 
being taken to bend the extremities quite flat, so that they 
may not be liable to puncture the India rubber used for ren- 
dering the joint water-tight. When the wires have been 
joined the tubing is brought forward so as to overlap the 
junction by about 2 inches, and is secured at each end 
upon the insulated wire by several laps of string, tightly 
bound round, (c c,) Fig. 57. In order to relieve the junction 
from any direct strain it is formed into a loop by tying 
together the insulated wires at a distance of a few inches 
from the point where the junction is made, as shown in Fig. 
57. 

The insulation covered by the India rubber tube should be 
well greased before the latter is pulled over it and tied. In 
doing this care must be taken to prevent the grease pene- 
trating to the metallic joint and thus impeding the electrical 
circuit. The grease is intended simply as an additional 
precaution against leakage of water. 

A very important matter to be attended to in making a 
joint, whether of a permanent or a temporary nature, is that 
the metallic ends should be perfectly clean — that there 
should be no oxide or impurity which would tend to in- 
crease the resistance to the passage of the current. To in- 
sure this they should be well rubbed with emery-paper just 
before the joint is made. 

In making this, or indeed any joint for submarine use, the Moisture to be 
great object is to exclude the very smallest ingress of watered " y 
or even moisture, which would at once afford a path for the 
current and cause a loss or, as it is termed, a leak in the 
cable; if, therefore, there is any external hemp or other 
covering, though which moisture might percolate in ever so 
small a degree, it must be carefully removed so that the 
India-rubber tubing may come in direct contact with the 
insulation at the point where it is tied. Care must also be taken 



142 

to make the whole very dry at the moment when the joint 
is made. 
Nicoiis metallic A very ingenious mode of making the wire portion of the 
joint has been invented by Donald Mcoll, esq., of Kilburn. 
His idea suggested itself in connection with his own sys- 
tem of underground telegraph-wires, but is equally appli- 
cable to the formation of joints of the nature required for 
submarine work and is very simple. He first prepares the 
extremity of one of the conducting-wires by forming it by 
means of a very neat and ingenious little instrument into a 
spiral twist, (see Fig. 58,) and the corresponding extremity 



fr. 58. 



of the cable to be connected being left straight, it is slipped 

in, the whole placed on a small anvil, and, by a single blow 

of a hammer, x^ressed so closely together that soldering is 

almost unnecessary, while the joint is renclered capable of 

standing a considerable tensile strain. 

Advantages and The great advantage of a joint insulated with this India- 

in S dfa a ru g bbe°r rill:)Der tubing is the facility with which it can be made at 

tube joint. an y j.- me an( j UD( ]_ er an y circumstances ; it is also very 

economical. The chief danger to it is the chance of a pro- 
jecting end of a wire perforating the India rubber and causing 
a leak, through which a loss of current would take place j 
care must therefore be taken to prevent such an accident. 
One mode in which the chance of such a contingency may 
be reduced, is by lashing pieces of wood on over the joint, 
outside the India-rubber tubing, to prevent any bending at 
that particular point. Under Mr. McolPs system, no pro- 
jecting ends are left in making the joint, and the chance of 
a perforation is thus reduced to a minimum. 
Dent's bottle Another very good joint, in many respects superior to the 
India-rubber tube, is that invented by Mr. Dent, of the 
chemical department, royal arsenal, Woolwich. It con- 
sists of two parts, viz, a cylinder or plug of vulcanized 
ludiarubber, aboutlinch in length, andthe same in diameter, 
through which three holes of sufficient size to admit the two 
insulated wires, (b &,) Fig. 59, and a tapering cylinder of 
wood, have been bored by means of a red-hot wire 5 and a 



joint. 



143 



stout glass tube(cc) about 1 inch iu diameter aud If inches in 
length, sealed at one end. 




Fig. 59. 






This joint is employed as follows: Each insulaled wire is 
passed through one of the holes in the vulcanized rubber 
cylinder, aud the clean bare ends of the metal wire are then 
twisted together and cut off short. If tape-covered wire is 
used the tape must be previously removed from about three 
inches of each wire. Into the third hole of the cylinder is 
loosely inserted a tapering plug of hard wood, (d) about § inch 
in diameter at the larger end, and 2 inches in length. The 
cyliuder, with the wires and plug, is then firmly pressed into 
the glass tube, and the wooden plug is afterward forced 
into the hole as tightly as possible, as shown in Fig. 59, 
which has the effect of forcing the India rubber against the 
sides of the glass cylinder and around the insulated wires. 
It is important that the India-rubber cylinder should fit 
tightly into the glass tube, and that the perforations made 
to receive the wire be not larger than absolutely necessary. 
A very small quantity of grease applied to the surfaces of 
the insulation of the wires, the plug, and the cylinder will 
greatly facilitate the fitting up of the joint and improve its 
efficiency . 

This joint is extremelv simple and economical, aud is easily Advantages and 

, , • i disadvantages o f 

made. A joint made on this principle was severely tried Dent's bottle joint 



144 



by being kept under a pressure of 18 feet of water, and 
tested at intervals with a reflecting galvanometer, under 
which, treatment no appreciable loss of insulation was indi- 
cated during a period of ten days. At the end of this time 







the glass cup was found broken, as if forced outward by 
pressure from the swelling of the plug or wedge, while it 



145 

remained submerged. It proved itself, however, an excel- 
lent joint as regards insulation. One of its defects is its 
inability to stand a tensile strain, in order to decrease the 
chance of which, as much as possible, the insulated- wire 
connections are tied together, as shown in Fig. 59. Another 
is the chance of the breakage of the glass by a blow, to ob- 
viate which the glass cup is covered with an India-rubber 
cap ; it is, however, easy to arrange it in such a manner 
that it may not be subjected to either of these contingencies. 
Another defect, above referred to, is the danger of break- 
ing the glass, by pressure exerted from the inside, in con- 
sequence of the swelling of the wooden plug after immersion 
in water. In order to obviate it, the plug should be made 
of box or some other very close-grained wood. 

Another, and much more elaborate, joint is that invented Gjov'er's joint, 
by Corporal Glover, R. E. It consists of an ebonite cylinder 
(«,) Fig. 60, fitted with two grooves to receive the uprights 
(b b) of a brass disk (c) whicli forms one end of the appa- 
ratus. This ebonite cylinder is bored through the center 
to admit the wires to be joined with their insulation, and the 
diameter of the bore is expanded, at each extremity, into a 
conical hollow to receive two similarly shaped plugs (d d) 
of vulcanite, which ' latter pass over the insulation of the 
wires and fit accurately into the cavities left for them j (h) 
shows a horizontal and (a) a vertical section through the 
ebonite cylinder. A brass disk (e,) similar to (c) but with 
holes to receive the brass uprights of the latter, is placed 
over the top of the ebonite cylinder, and is held firmly on 
by screws (//) passing on to the uprights. A small pro- 
jecting ring (g) on the lower disk (c) and a similar arrange- 
ment on the upper one (e) keep the vulcanite plugs from 
being forced out laterally when pressure is applied. A me- 
tallic connection having been established by twisting the 
conducting-wires together, the outer protecting covering 
having, as before, been carefully removed, the base wire is 
drawn into the center of the ebonite cylinder, the screws 
(//) are tightened, and the vulcanic plugs are driven for- 
cibly into their respective cavities, making the whole water- 
tight. A little grease carefully applied to the insulating 
material at the points of pressure will in this, as in other 
similar cases, improve the insulation of the joint. 

The defects of this joint are its high cost and the uneven Defect of 
bearing given by the two screws used in tightening up; tLiis Glover ' s J° int - 
latter might, however, be obviated by the employment of 
three screws, in a triangle, instead of two, by Vhich all side 
10 



146 



B e a r d s 1 e e's 
ioint. 



motion, after the process of tightening up, would be obvi- 
ated. 

Another joint is that said to have been invented by Mr. 
Beardslee, of New York, but bearing the name of Goodyear's 
patent on a specimen left at Chatham by him. It consists 
of an ebonite cylinder, (a,) Fig. 61, with closed ends, one a 
fixture and the other fitting the cylinder with a screw (b.) 




Fig. 61 



Each end has a perforation of sufficient size to admit the 
insulated wires (c c) which are to be connected. The bare 
extremities of the wire having been cleaned to the extent of 
about finch, each one is passed through one of the perforations 
in the joint, as well as through a disk of vulcanized rubber 
(d d) of f inch thick, and one of metal (e e) J inch thick. The 
bare extremities of each conductor are secured by spreading 
them out upon the metal disks, and these are then brought 
into close contact in the interior of the ebonite cylinder by 
screwing up the movable end thereof as tightly as possible. 
specially appii- This joint is specially applicable to a strand conductor, 
conductor. composed of a number of fine wires, which may be separated 

and spread over the metal disks so as to insure good con- 
tact. 

The usual precautions, as to the removal of any outer 
protecting covering and greasing the insulation, must be 
borne in mind in forming this joint. 

It is particularly necessary, in employing this joint, to 
guard against direct strain being thrown upon the wire 



147 

extremities which are inclosed, as they would be even more 
liable to be drawn out of the cylinder, in which they are 
rigidly fixed, than in the case of other joints; the electrical 
connection, in this case, being formed by the simple contact 
of the two metal disks and not by twisting the wires together. 
The wires should therefore be firmly braced together at a 
short distance from the point of juncture, as shown in Figs. 
57 and 59. 

The defects of this joint are its inability to stand a ten- Defects of 
sile strain, which would tend to draw out the wires, or S0 Beardslees J° int 
far separate the metal disks on which the wires are spread 
out as to break the metallic contact, and thus interrupt the 
current, and that the wires to be connected cannot be sol- 
dered. 

Another joint is that invented by Quartermaster-Sergeant . Matnieson's 
Mathieson, E. E. It consists of two ebonite cylinders, (a a,) 
Fig. 62, perforated to receive the cables to be connected, 
the opening at the outer extremities being just large enough 
to admit the insulation of the wire to pass freely, while the 
inside is larger, thus forming shoulders against which thick 
perforated vulcanite rings (b &,) encircling the insulation, are 
placed. Within these cylinders is an ebonite tube with 
wedge-formed ends in contact with the vulcanite rings, 
within which the wire connection should be placed. The 
center of tube (c) is of square section, and fits into a hollow 
of similar form in the cylinder (a a ;) the ends of the tube are 
of circular section ; the object of the square center is to 
prevent the wires to be connected being twisted round and 
round during the process of tightening up, as any torsion 
of this nature would be liable to disarrange the metallic 
connection within or to injure the insulation. A coupling- 
screw, (<?,) with a shoulder to catch a corresponding shoulder 
on one of the ebonite cylinders, and a corresponding screw 
on the other, completes the arrangement. 

Portions of the coupling-screw, and one of the ebonite 
cylinders, are made of hexagonal form, to fit a couple of 
spanners to be used in tightening up the apparatus when 
greater force than that which can be applied with the hands 
is necessary. It is easily seen how, by tightening up the 
coupling-screw, the two ebonite cylinders may be drawn 
together and the internal tube forced upon the vulcanite 
disks, making the whole water-tight. 

To make an insulated joint with this apparatus, the coup- To make a joint. 
ling (d) is unscrewed as far as possible without separating 
the two parts, (a a,) and a little grease is applied to the threads 
of the screw ; the whole apparatus is then slipped bodily 



148 

on to one of the insulated cables to be connected ; the insu- 
lation of each cable, having been previously rubbed with a 
little grease, is then carefully tapered off to a blunt point 



Fig. 62. 





and rubbed with a little grease, taking care that this grease 
does not extend to the metallic conductor. The extremi- 
ties of the metallic conductors, having been carefully cleaned, 
are next twisted together so as to leave as short a length of 
naked wire as possible, care being taken that the diameter 
of the two wires, when twisted together, does not exceed 
that of the insulation. The exposed metallic joint is next 
drawn back into the center of the connector, which is 
then screwed tightly up with a spanner and the India- 
rubber packing so firmly wedged round the insulation 



149 

as to exclude damp most effectually from the bare con- 
ducting- wire in its center. 

If the connector be unscrewed and the ends of the wire rat T u ^^ e a K 
carefully drawn out, the same apparatus may be used any more *« once - 
number of times, provided it has not been injured by the 
explosion of a mine, If the inside be wetted it must not 
be used again till thoroughly dried ; especial care is neces- 
sary if it has been accidentally wetted with sea-water, the 
latter being a better conductor of electricity than fresh 
water. 

When the cable is covered with an outer protection of 
tape, hemp, or any similar substance, it is necessary to 
remove this carefully from the vicinity of the joint, as the 
damp would penetrate through the fibers were it allowed 
to remain. 

In order to test the efficiency of this apparatus, a piece of JJgjgSg?. "' 
cable, which had previously been tested for insulation and 
found good, was cut into nine pieces and joints made at the 
cuts with Mathieson's joint, thus forming eight points through 
which the current might leak. This was sunk to the' bot- 
tom of the river Med way, a depth of 36 feet, and tested from 
day to clay for a period of more than two months, with 48 
Daniell's cells, and an astatic galvanometer, without show- 
ing any indication of leakage of current. 

This joint possesses considerable tensile strength, but 
were it likely to be submitted to any considerable strain, 
it is nevertheless a good precaution to form a loop in the 
cable, as recommended for those previously described and 
shown in Figs. 57 and 59. 

When an insulated cable has an outer protecting covering Matwesous joint 
of wire, a modification of Mathiesoirs joint must be used, wire protecting- 
This is shown in section, Fig. G3; a simple addition in the 
shape of two ebonite tubes (a a) made to pass easily over the 
outer protecting covering, with India-rubber cylinders (b b) 
also fitting over the same, in addition to those in contact 
with the ebonite tube covering the metallic joint of the 
conducting- wires, is all that is necessary. It is easily seen 
how, by simply drawing the parts of the apparatus together by 
means of the coupling-screw, everything may be made 
water-tight and consequently insulated as before. In making 
a joint on a cable with an outer protecting covering of wire, 
this latter must necessarily be removed, and a weak place, 
at which the cable would bend easily, would be formed. 
The joint described, by gripping the outer covering beyond 
the actual point of connection, prevents any such bending 



coverins 



150 



with the danger inseparable from it of piercing the insula- 
tion by a projecting wire. 



Fig. 63. 



These joints must be made 
to fit the insulation of the 
cables they are intended to 
connect with a certain amount 
of accuracy. They must be 
sufficiently loose to slip easily 
over it, before being screwed 
up, and the limit, within which 
a joint made for one size of 
cable may be used for a 
smaller one, is dependant upon 
the extent to which the India- 
rubber cylinders may be com- 
pressed, so as to fill up the 
vacant space and make the 
joint water-tight. 

When there is no iron in 
contact to be damaged by the 
electrical action set up by the 
sea- water, the coupling-screw 
and outer portions of this joint 
may be made of gun-metal, 
which gives greater strength 
than ebonite. 

Mathieson s is decidedly the 

MkSESSP joint best ° f a11 the temporary 
joints described, possessing, 
as it does, excellent insulating 
qualities, great facilities for 
making or detaching a con- 
nection between two cables 
in a short s^ace of time, and 
being capable of standing a considerable tensile strain. In 
many situations it may conveniently be used to supply the 
place of a permanent insulated joint, to which, as far as 
insulating qualities are concerned, it is quite equal, and to 
which, where facilities for examination are required, it is 
superior. 

All the temporary joints, above described, were tested 
for insulation, similarly to Dent's, (see page 144,) and all 
stood the test, which was a very severe one, remarkably 
well. Mathieson's was again more severely tested, as 
already described, with very satisfactory results. 




Experiments to 
test temporary 
joints. 



CHAPTER IX. 

SUBMERGING MINES, ETC. 

We now come to the mode of laying down the mines in 
snch a position that they shall be most effective, and at the 
same time so disposed that the explosion of one shall not 
injure the cables, circuit-closers, &c, in its vicinity. 

The position of the mines having been first determined, ti0 ^ o?miLs P ° si 
should be marked off by means of buoys, arranged to corre- 
spond with the charges to be subsequently placed in position, 
and points on shore to guide the vessels employed in laying 
them. The moorings may either be first placed in position, 
and the mines and circuit-closers hauled down to them, or the 
whole (moorings, mines, and circuit-closers) may be launched 
overboard, attached together in proper relative position, at 
the same time. In deep water it would probably be found 
preferable to adopt a system of hauling down to moorings 
previously i^laced, while in shallow water it would, under 
certain circumstances, be found quicker and more convenient 
to adopt the latter mode of proceeding. The cases ready 
charged, and with the electrical cables, &c, attached, having 
been lowered into position at such intervals as may be 
required, according to the size of charge to be used, and 
each carefully buoyed with a numbered buoy, the paying out Paying out eiec- 
of the cables may be proceeded with. The electrical cable 
attached to each, having been previously arranged on a 
drum, should be placed on board a pinnace or launch, which 
should proceed directly to pay it out in a line as nearly as 
possible perpendicular to the line of mines. Each boat 
should be provided with a small testing-battery and astatic 
galvanometer, by which the insulation and electrical resist- 
ance of the system should be tested at intervals, from the 
moment of submerging the mine till the other extemity of 
the cable is safely lodged in the testing-room. Any defect 
likely to cause a failure in firing at the proper moment 
would, in this way, be immediately discovered during the 
operation of submergence. As the boat, in paying out the 
cable, passes the position marked out for the second or 
covering line of mines, care should be taken to have it, as 
nearly as possible, midway between two adjacent mines in 
this line, to prevent the cable beiug damaged by the explo- 



152 

sion of the inines»in this line; the mines of this second line 
would, as stated in page 23, be so placed as to cover the 
intervals of the first. In passing this line the position of 
the electric cables should bejnarked off by buoys as a guide 
to those laying down the second line of mines, which, as soon 
as the work of the first has proceeded so far, may at once be 
commenced. In order to distinguish between the buoys 
marking the positions of the mines from those indicating the 
directions of the cables, different colors might be used ; as, 
for example, those attached to the mines might be painted 
red, and those in connection with the cables black. As the third 
line of mines would be placed to cover the intervals of the 
second, it would be necessary, after proceeding in a direct 
line for about 100 yards in rear of the second line of mines, 
to change the direction in which the cable is to be laid by 
carrying it perpendicular to the direction hitherto followed, 
till a point directly in rear of one of the mines of the second 
line is reached, when it should again be turned inward, and 
would be in a position to pass safely through the center of 
an interval between two mines of the third line, as it had 
previously passed through those of the second, so as not to 
be injured in the event of their explosion. In passiug this 
third line of mines it should be again buoyed for guidauce 
in laying the mines belonging thereto, and so on till the 
extremity of the cable was connected to its corresponding 
wire, if a multiple cable were used for any portion of the 
distance, or if each were to be taken in singly, till safely 
landed in the fort in which the operating-room is placed, 
when it should be attached to its proper binding-screw, and 
its insulation and resistance carefully tested and registered. 
Lines of cables The same process would be gone through with every 

siWefromchar P es charge, the utmost care being taken so to lay the cables 
that they shall be as far as possible away from the mines 
in the vicinity of which they may be required to pass, so as 
to give the least chance of injury from the explosion of the 
latter. By the arrangement above described they would 
also be in a favorable position for underrunniug and pick- 
siack to be ai- ^ n S U P> should such an operation become necessary. A cer- 

lowed. tain amount of slack should be allowed in laying the cables to 

facilitate picking them up for examination and repair. This 

amount of slack will depend on the depth at which a cable 

is submerged. 

positions of The position of each charge should be identified by means 

tmeTbV o b earings of bearings taken by two theodolites, from points well si t- 

pTan marked « on a uated for the purpose, and marked in position on apian, 
with the number of each mine, as a guide to facilitate its 



153 

discovery at any future time. This done, and the whole 
system having" been proved to be electrically correct, all the 
surface-buoys should be removed, to prevent any indication 
of their position being given to an enemy. Dummies to 
deceive an enemy may be judiciously arranged in a manner 
not too ostentatious, but they should never be placed in 
such a position as might, in ever so remote a manner, lead 
to the discovery of a real mine. Fig. G4 gives a general 
idea of the position of the cables if laid down on the prin- 
ciple described; the cables are indicated by the dotted 
lines (c c c, &c.,) the mines of the system are shown at (m 
m m, &c.) 

Fig. 64, 



m 



01 



nu 



rrv 



7TU 



m/ 



TTh 



I Q 






nv 



\c 



rrv 



TJV 



O O O 



rrv 





\C 



TTh 







• c i 



m> 



9 ! 9 ! 9 



\c \ 


rrv \ 


Q j 


\c ! 


i 1 ' 



771 



C v 



W* 



rrv 



I 



77V 



rrv- 






nv 



TV 



O I o 



II / 

ll / 



•^ 



\ >! 



/// 






'/,' 







They should be laid, as far as possible, parallel, and never 
be allowed to cross directly over each other, otherwise the 
operation of under running will be much complicated. 



154 

Electric cables The arrangement of the cables above described is that in 
flank of mines, which the shortest possible length would be consumed, and 
would, perhaps, be the safest from discovery by an enemy's 
boats. In certain cases, however, it might be convenient 
to carry them by a detour to the fort, as for example round 
the flank of the second and third line of mines, and there 
would be no difficulty in this, always bearing in mind that 
they should, in the first instance, be carried directly back 
for about 100 yards, so as to be safe from injury due to the 
explosion of their own line of mines, and that their subse- 
quent course should be so arranged as to keep them safe 
from damage from the explosion of any other mine in the 
system. 
cables to be pro- In selecting any line to betaken, places where the cables 
of C sea. n s would be subjected to a wash of the sea should be, as much 
as possible, avoided, and when it becomes necessary to 
place them in positions where they are necessarily subjected 
to the friction and rubbing consequent upon the motion of 
the water, special precautions must be employed for their 
protection. 
position of eiec- The confederates used all sorts of devices to conceal their 
concealed* *° be electrical cables, such as laying dummies, making consid- 
erable detours inland, &c, and such precautions must always 
be taken when required by peculiar circumstances. It is 
impossible, however, to lay down any rule for such cases, 
which must be left to the ingenuity of those in charge of 
• the mines, who will be best able to judge of the capabilities 
of any particular position. 

The only general rule which can be laid down for guidance 
in such circumstances is to place the cables where they can 
be subjected to the greatest amount of supervision, and 
where they can be most easily defended from injury by an 
enemy. 
Mode of placing The following proposed mode of placing submarine mines 

mines in position, ° . 

proposed by Lieu- in any given position, and of dealing with the cables in con- 
tenant Anderson, . , , , -..„,. -, i ■, t -u 

k. e. nection with the different charges, has been drawn up by 

Lieutenant Anderson, E. E., and is applicable where the 
land or river banks are conveniently situated for erecting 
the poles. 

The direction of a line of mines, to be placed across a 
channel, may be determined by two poles previously erected 
on the shore, as shown at (a and &,) Fig. (35. The arrange- 
ment to give the intersections on the above-mentioned 
alignment, where each mine is to be placed, is shown by the 
poles marked (c, and 1, 2, 3, 4, 5, G) to correspond with the 
numbers of the mines. 



S 6 




Fig. 65. 



6 , 



5 ; 4 4 ^ 2 N JL 




first mine. 



155 

The proposed mode of placing the charges in position is 
as follows : 

Soundings are first taken at the required points, and the 
length of inooring-line for eacli charge determined accord- 
ingly. The anchor is to be suspended from the davit of the 
working pinnace, and everything made ready to let it go 
with a run. The electric cable to be stoppered to the inoor- 
ing-line between the charge and the anchor, and a strong 
mooriug-cham or wire rope to be provided to connect the 
charge to the circuit-closer, so that, by this chain, both the 
charge and anchor may be raised if required. The electric 
cable, between the circuit-closer and charge, should be stop- 
pered to the chain or wire rope in the same manner as from 
the charge to the anchor. The length of the electric cables, 
from the anchors of the different charges to the point (d) 
on which they converge, would vary according to the posi- 
tion of the charges with regard to the center line of the 
channel. Each electrical cable to be coiled on a small port- 
able drum, so that it may be easily moved in and out of the 
working pinnace. 

To place the first charge the pinnace (with the anchor ^Topiuce the 
connected with the charge and circuit- closer by moorings 
of proper length, as above described, and suspended by the 
davits at the stern) would be turned out into the exact 
alignment given by theline(a &,) proceeding only fast enough 
to obtain steerage-way ; as soon as the stern of the pinnace 
arrived at the intersection given by the alignment (e 6,) the 
order would be given " let go," and immediately anchor, 
charge, and circuit-closer would be drawn down into position. 
The electric cable would then be payed out, at first directly 
away from the charge, and finally taken to the boat (d,) 
which had been previously anchored in a position 100 yards 
or more in rear of the center of the part of the channel to 
be defended. When many charges are to be placed in the 
same line, it is recommended, in order to avoid the use of 
long cables and consequently unwieldy drums, that the 
cable from the charge 6 should only be long enough to reach 
to the boat (d,) in which the end of this cable is for the time 
being secured. The next charge, with all its attachments 
complete, having been arranged as before, the pinnace 
would again slowly cross the channel along the alignment 
(«&,) till her stern arrived at the intersection 5 with the pole 
(c,) when the anchor would be let go, and the cable of this 
charge carried in the same manner to the boat {d.) Thus all 
the charges up to Xo. 1 would be similarly deposited into 
position, and their cables carried as far as the boat (d.) 



156 

Tests t* be made Tests for continuity and insulation should be made as soon 
gence. 8r " as each electric cable arrives at the boat (d.) When a multiple 

cable is to be employed for the main conductor, (and if 
battery power were always used for firing there would be 
no objection to the use of such a cable,) it would now be a 
simple matter, by means of insulating* ebonite joints, to con- 
nect each cable to its corresponding main conductor; or, if cir- 
cumstances permitted, it would be advantageous to establish 
at this point of the electrical circuit a test-box, into which all 
the cables from the charges might be carried, and in which 
the connections with the main conductor might be made. 
This test-box, which should be of iron, and supplied with 
a lid screwed firmly down to the body of the box by means of 
nuts and screws and a substantial washer, should be suffi- 
ciently heavy to insure its not being disturbed at the bottom 
of the channel by the force of the tide or current. A test- 
box would facilitate examination for the discovery of any 
leak or fault that might occur in the circuit. This could be 
done without disconnecting the other wires in the test-box; 
and in the event of any one charge being exploded or car- 
ried away, it would only be necessary to renew the cable 
from the test-box to that particular charge. Where the 
use of a multiple cable is impracticable, each must be car- 
ried separately into the fort from which the system is to be 
controlled. It would, probably, be most convenient to have 
the drum of the multiple cable or the separate drums of the 
single cables in the fort, and lay the cable or cables there- 
from to the anchored boat (d.) This operation might thus be 
carried on simultaneously with that of mooring the charges. 
The objection to it in the case of cables carried in singly 
would be the joint to be made in the boat, (c?,) for which 
reason it would, with single cables, be preferable to preserve 
them in one continuous length and lay them from the boat 
(d) to the fort, after the previous portion of the work had 
been completed. If single cables are used, they should be 
payed out in parallel lines so as not to cross each other, in 
order that each might be conveniently uuderrun and ex- 
amined, if required, without fouling any of the others ; or the 
single cables might all be tied together with spun yarn and 
laid out as one. It is certain that if some systematic manner 
of placing a series of cables along the bottom of a channel is not 
adopted they will become entangled with each other. There 
is, however, an objection to their being laid out close to 
each other — that an enemy grappling in that direction would 
be certain to catch all the cables together. 



157 

When everything has been completed the boat (d) should ah marks iudi- 

, . . . eating position of 

be removed, its position having been previously caretully miues to be re- 
determined by bearings, to facilitate any future search for move( " 
the cables at that point. The poles or marks (a, b, c, 1, 2, 
3, 4, 5, and G) should also be removed, their positions having 
been carefully marked, so that no indication of the locality 
of the mines may be given to an enemy. 

As there would nearly always be more than one line of 
mines, it would be necessary to repeat this process for each, 
for which purpose we should have to establish a separate 
set of poles to mark the intersections. 

In working from a chain or hawser, on which the distances 
have been marked, as described at page 75, the weight of 
the working-pinnace holding on to the chain at the required 
position produces a certain amount of sag, greater in pro- ' 
portion to the length of the directing hawser, and this sag 
must be taken into consideration, and as a check a couple 
of poles, as at (a h,) Fig. Go, or two buoys, where poles could 
not be used, would be found convenient. For short dis- 
tances, across .the Medway, for example, the arrangement 
with a directing hawser works with sufficient accuracy. 

The next point to be considered is the best mode of. intro- § iSSSwWeAnto 
during the cables into a fort or sea-battery. In doing so afort 
they should be protected to the utmost, not only from injury 
by an enemy, but from the friction and rubbing necessarily 
caused by the wash of the sea. Bearing these objects in 
view, advantage must be taken of local circumstances which 
will present an endless variety of conditions, which must 
be met by expedients suited to the nature of each particu- 
lar case. A great deal must therefore be. left to the discre- 
tion of the officer in immediate charge, and very few gene- 
ral rules can be laid down. As already stated, it is, however, 
necessaiy to carry them into such forts and defensive posi- 
tions as are likely to hold out longest in any system of 
defense, and not, as a matter of course, into those nearest 
to them. They must be covered to the utmost from an 
enemy's fire, and, as far as possible, be protected from his 
interference in any way, as his great object' would be to 
break and destroy the electrical circuit; when exposed to 
rubbing and motion from the wash of the sea, they should 
be provided with an outer protecting covering of iron wires, 
copper tape, or something similar, as already described in 
treating of the description of electrical cables best suited 
for the purpose, and should be further, as far as possible, 
covered and placed in sheltered situations. It is a great 
matter in such situations to weight a cable well, and a good 



158 



expedient would be to attach it to a heavy chain. This 
would be a good plan to adopt in carrying it over shallows 
not only near its entrance into a fort, Uut wherever they 
may occur along its line. 
Modification of The following design for introducing the cables into a 

design by Lieuten- CT 

antw. g. Nichoi. fort, is a modification of one proposed by Lieutenant W. G. 

son, R. E. r *r j 



Fig. 66. 




Nicholson, E. E. ; it is applicable to the particular section 
shown, and serves to give some idea of the essential points 
to be kept in view, while the details of each particular case 



" 






159 

must, as already stated, be modified according to local cir- 
cumstances. 

A plan of the proposed mode of introducing the wires is Testing - room, 
shown in Fig. (W y and a section in Fig. 67; {a) is a testing- age, and hood? 88 
room, into which all the cables must be brought, and where 
the apparatus, by which the whole system is controlled, 
is arranged; (b) is a store adjoining; (c) is a shaft 2 by 4 feet, by 
which access is gained to the gallery (d) cut through the 
outer masonry of the fort; the shaft (c) is provided with a 
ladder ; (e) is an iron-plated hood carried down to the level of 
the bottom of thesea; theiron plating is carried sufficiently far 
below low-water mark to secure the hood from the enemy's shot; 
(/) is a gun-metal diaphragm, through which each cable passes 
by means of an apparatus precisely similar to Mathieson's 
joint ; this diaphragm need not be water-tight, and is only 
intended to prevent the wash of the sea rushing violently 
into the passage (d) and thence in the testing-room, as would 
be the case without it in stormy weather. A man-hole (g) 
gives access to the hood and permits the sea, rushing in 
through the hood and checked by the diaphragm, (/,) to escape 
without bursting in the latter. 

The cables, on arrival at the foot of the hood, are carried Frames to carry 
in on a system of frames, as shown in section, Fig. 68. 
These are placed at intervals along the hood and gallery, 
and are provided with four shelves or compartments, each 
carrying 20 cables, laid in a separate groove and numbered, 
making a total of 80 for the whole. These frames should 
be of gun-metal ; iron is too apt to oxidize, and wood, which 
would be alternately in water and air with every rise and 
fall of the tide, would be liable to rot and render constant 
repairs necessary. The frame- work occupies half the breadth 
of the gallery, leaving the other half for access and exami- 
nation of the cables. On arrival at the shaft (c,) each twenty 
cables are collected together and carried up along the sides 
of the shaft to the testing-room. Should it be necessary to 
carry more than 80 cables into the fort, it would only be 
necessary to arrange a series of hooks, on the far sides of 
the frames, on which several additional lines could be sup- 
ported. 

The floor of the testing-room should, if possible, not be LeV ei of floor of 
less than three feet above high- water spring tides, other- Sotof hood. and 
wise, it would be very liable to be flooded by the wash of 
the sea in rough weather, for even with the diaphragm, (/,) 
there would still be a certain amount of motion in the water. 
Where possible, the outside of the hood should not be less 
than 10 feet below low-water spring tides, because at such 



160 

a depth, except on extraordinary occasions, there would be 
comparatively little motion from the wash of the sea. 

Fig. 68. 




To make con 
nection with ex 
terior. 



(Section of gallery showing 1 frame. Number of cables, 80.) 
The man-hole (g) gives access to the hood; for the manip- 
ulation of the cables, it would only be necessary to go in at 
low water and establish a communication with the exterior 
by pushing a buoy beyond the outside of the hood by means 
of a pole of sufficient length $ the buoy, on floating to the 
surface, would carry a line wifch it, which would be all that 
is necessary, and by it a cable might" be hauled in or out as 
required. This would, in a great many cases, do away with 
the necessity of employing a diver, though it would, never 
theless, be necessary that a diver be at hand where any very 
extensive system of submarine mines may be used for de 
tensive purposes. 
identity of each In passing from the outside to the testing-room, the iden- 
fuiiy e pr eHerved re tity of each cable must be carefully preserved throughout 
by means of a number, and each would be finally attached 
to a binding screw or connection similarly numbered, so that 
any particular one might be easily picked out if required. 



161 

Much care would be necessary to prevent confusion in carry- 
ing in the electric cables, in the first instance. 
The arrangement of a system of submarine mines in lines Disadvantage 

, . , . j_ of an arrangement 

possesses one serious disadvantage, viz, that an enemy, f mines mime. 
having once ascertained the position of one mine of a line,, 
either by its explosion, or by any other accidental circum- 
stance, would know within limits where the others were to 
be looked for. In order to obviate this disadvantage, it Mode of obviat- 

. . ing this disadvan- 

would always be necessary to scatter a few mines at irregtt-tage by advanced 

, , . ,. i mines at irregular 

lar intervals m front of the advanced line — to put them, so intervals. 
to speak, in the position of skirmishers, retaining the line- 
formation for the main defense. These advanced mines 
might either be simply electro-self-acting, or arranged for 
ignition on the same principle as those of the main system, 
as circumstances required. 

The first object of an enemy would be to clear a passage Defense of 
J J l o Tuiues from drift . 

of sufficient width through the system to enable him to passers, 
freely in, and for this purpose he would probably employ 
drifters, with or without dragging-grapnels, for the purpose 
of either firing some of the charges by striking the circuit- 
closers, or grappling and destroying the electrical cables 
and other gear. These drifters might be boats allowed to 
float in with the tide or wind, and need not necessarily con- 
tain any men, so that the loss of human life would not be a 
certain consequence of their destruction by the explosion of 
a mine. In order to stop such a system of attack, light booms Defense by 
or strong fishing-nets would no doubt be extremely useful, and nets? 9 an s ing ' 
should be employed wherever circumstances admitted. To 
stop drifters with dragging grapnels, it would seem to be a Defense by 
good plan to lay three or four heavy chain-cables at inter- C hS. m 
vals across the channel in advance of any system of mines. 
The grapnels would catch in these, and the weight of the 
chains would be sufficient to bring up the drifters before 
arriving at the system of mines. 
The night would unquestionably be the safest time for an Mines must be 

, ,. „ ,. . , , ., , -, watched at night. 

enemy to carry on operations of this nature, and it would 
be necessary to employ boats to row guard in order to watch 
his proceedings. The mode of communication with these 
boats is a matter of considerable importance, and some 
means of rapidly transmitting intelligence is absolutely 
necessary. This can, of course, be done by the army and 
navy system of flashing signals, but the lights, in such 
cases, would be a disadvantage, as they would indicate the 
position of the guard-boat. In order to obviate this, a sys- Electrical * y s- 

' tem of communi- 

tem has been devised by which a boat rowing guard can be cation between a 

° fort and guard- 

put in electric telegraphic communication with a fort or boat. 
11 



162 

guard-ship, by simply paying out an insulated wire attached 
to a telegraph instrument in the fort or ship, and carrying 
a second telegraph instrument on board the boat. The sys- 
tem is so arranged that no electrical batteries need be carried 
in the boat, the whole of them being retained at the headquar- 
ter telegraph station. The instrument in the boat would be a 
simple Morse sounder, so that no light of any sort would be re- 
quired to read the message. The telegraph instrument at 
the headquarter station might either be a Morse sounder or 
a Morse recording instrument, and, when the latter is used, 
the system has been so arranged that all messages, both 
those emanating from the headquarter station and those 
received from the boat, may be recorded for future refer- 
ence. By this means messages can be transmitted either 
by the Morse telegraph alphabet or by any signal code, and, 
when the latter is employed, any man who has been 
taught the army and navy system of signaling can learn 
to use these instruments with very little practice. The ap- 
paratus has been used for some time in the river Med way, 
in carrying on our submarine mining operations, and answers 
perfectly. Should the guard-boat be chased, it would be only 
necessary to detach the electric cable from the telegraph 
instrument and throw it overboard, with a buoy and line 
attached to it, and pull away. It could be recovered at 
leisure. 

Several systems have been devised for illuminating chan- 
nels at night by means of the electric light, the Drummond 
illumination oflight, magnesium light, &c, and there is no doubt that, 

channels defended , " , . , , , -, -ii-ii t -i 

b y submarine where practicable, such devices should always be used. 
The action of the several lights named is too well known to 
render it necessary to describe them here, but there is one 
device which might be easily made use of in connection 
with a guard-boat. A substance, producing by its ignition 
a very bright light, (magnesium, for example, would be one 
of the best,) might be arranged on a float, and a guard-boat 
carrying a few of these might, if chased, ignite and throw 
one out. The apparatus should be provided with a short 
fuse, to enable the guard-boat to get a little distance off 
before the actual light burst out. In this way an enemy's 
vessel might be seen and fired on by the guns of a battery. 
Boxer's parachute shells, or any similar device, would also 
be useful for illuminating purposes. 



CHAPTER X 



ELECTRICAL IGNITING AGENTS. 



Firing at will. 



Wheats tone's 
magnetic explo- 



Having carried onr electrical cables into tbe fort, the next 
point to be considered is tbe agent by wbicb tbe mines sbali 
be ignited. 

Ignition may be effected eitber at will or by a self-acting ignition at win 
arrangement, tbe vessel, in tbe latter case, berself completing ° c { £l cnrcuit ' 
tbe circuit by means of a circuit-closer. Tbe means employed 
in firing at will may be a magneto-current, frictional electri- 
city or battery-power ; when a circuit-closer is used, battery- 
power only is available. 

First, with reference to the employment of a magneto-cur- 
rent. Several instruments for the production of a current 
of this nature have been devised, and perhaps the most 
beautiful and ingenious of them is that of the well-known 
electrician, Professor Sir Charles Wheatstone; a description 
of it, which is given in the printed Course of Instruction in Her? 
Military Engineering, published by authority, page 152, will 
serve as a key to the construction of all instruments of this 
nature. 

The mode in which the uneven succession of currents, 
produced by a magneto-induction apparatus, and which is 
not given in the Course of Instruction in Military Engineering, 
is overcome is very ingenious. Sir Charles Wheatstone has 
placed two bobbins on each pole of the magnets instead of 
one, by which arrangement he obtains the result shown in 
Fig. 69, where, if (n n', s s') be tbe 
bobbins, and (a) the armature revolv- 
ing in front of them, the latter is so 
arranged that, at the moment when it 
is breaking contact with (n 1 ) and («,) it 
shall be making contact with (n) and 
6-',) and thus the difficulty occasioned 
by the uneven succession of currents, 
which would occur if only one pair of bobbins were used, is 
got over; for tbe coils are so arranged that, for example, in 
the position of the armature shown, the larger or breaking- 
contact current, induced in the coils (n) and(s',) is transmitted 
in the same direction as the smaller or making-contact cur- 



Fig. 69. 




164 

rent, induced in the coils (n f ) and (.9,) and thus we obtain an 
even succession of currents, iirst in one direction and then 
in the opposite; for, as the armature continues to revolve, it 
tirst makes, and then breaks, contact with the opposite pairs 
of bobbins simultaneously and with great rapidity. 

The defect of this instrument is the small quantity of the 
electrical current induced, which renders it necessary to 
have very perfect insulation throughout the whole of the 
connections. 
Arrangement of Fuses to be fired with this apparatus must be arranged in 
stone's exploder, simple divided circuit, and the number of charges, which 
may be fired in an^ given group, depends on the extent of 
the leakage or loss of current through the ends of the con- 
ducting-wires laid bare, after any given number of mines in 
such group have been fired. Though practically simultane- 
ous, the charges are really fired in extremely rapid succession, 
and as each explodes a greater surface of bare wire is exposed, 
and brought in contact with the surrounding earth or water 
in which the mines are placed. When this bare wire amounts 
in the aggregate to a conducting surface, sufficient to carry 
away a large proportion of the current generated, no further 
fuses will be exploded. The eonducting-power of water, 
especially salt water, is much greater than that of earth, and 
consequently, though as many as ten fuses may be fired with 
this apparatus in dry earth, we cannot reckon on igniting 
more than four with certainty in salt water. 
Beardsiee's mag- Mr. Beardslee, of New York, has designed an instrument 
pSdinrmacbine X of somew r hat similar construction to Wheatstone's, capable 
of producing a greater quantity of electricity with less electro- 
motive force. The general principles of this instrument are 
similar to those of Wheatstone's. 

It consists of a compound magnet, (said to be made of cast 
iron,) provided with ten arms arranged like the spokes of 
a wheel, each arm being composed of four separate magnets 
about i inch in thickness. It is mounted on a central axis, 
upon which it may be made to revolve with very great 
rapidity, by means of wheel-gearing and a handle. 

The armatures with their coils of insulated wire (about 
24 gauge) are fixtures; they are arranged in two circles, 
and are placed in as close proximity to the arms of the mag- 
net as is possible without touching them, one coil being- 
above and the other below each arm. The coils are con- 
nected together in four series of five each, by means of two 
insulated wires; each of these terminates in a separate 
metal plate, whereby each is brought into distinct connec- 
tion with the external poles of the machine, (communicating 



165 



with the condueting-wires.) By this arrangement each set 
of poles of all the coils is connected with one pole of the 
machine. The machine is inclosed in a box, in which it is 
very firmly fixed by means of a stout iron frame- work. On 
an inner lid of the box is the handle, by the movement of 
Avhich the magneto-electric current is developed 5 the binding 
screws, which are immediately over the inclosed pole-plates, 
and which receive the conducting and earth wires; and 
lastly a key arrangement, by the movement of which, at the 
required moment, when the magnet is revolving at its max- 
imum velocity, the electric current is passed to the binding 
screws, and thus to the charge which is to be exploded. 
An outer lid incloses the entire mechanism, so that all parts 
are protected from injury during transport. 

It was especially adapted for use wilh Beardslee's fuse. 

Kindred instruments to the above, called dynamo-electri- pynamo-dectii- 

7 ^ • cal machines. 

cal machines, are manufactured by Messrs. Siemens Brothers, 
of Charltou, and Mr. Ladd, of Beak street, Loudon. An 
important difference exists in these instruments as com- 
pared with the ordinary magneto-induction apparatus, 
namely, that they are independent of permanent magnetism 
for the current induced. 

The instrument made by Messrs. Siemens is very similar Siemens' dyna- 
in its arrangements to any magneto-electrical apparatus of ™ws. ctncal ma ' 
ordinary construction, but in it the permanent magnet is 
replaced by a piece of soft iron, (c,) Fig. 70, round which a 

coil of fine insulated wire is 
wound as at (a a;) (b) is a Sie- 
mens armature of soft iro, 
on which a coil, in metallic 
~-\ connection, through a com- 
mutator, with the -coil (a) is 
wound. When this arma- 
ture is made to revolve rap- 
idly, the residual magnetism 
in the horseshoe-formed piece 
of soft iron (c) induces a series 
of currents of electricity in 
the coils of the armature; or if there is absolutely no resi- 
dual magnetism in (c.) it is only necessary to touch it with a 
permanent magnet for a moment, when beginning to move 
the armature {b.) The currents thus induced in the coils of (b) 
circulate through the coils (tf «,) and increase the magnetism, 
which in its turn re-acts on the coils (5,) and induces a stronger 
series of currents. In this way the one may be made to 
r e-act on the other, till (c) becomes a powerful electro-magnet, 



&'?. 70. 




166 

and a very considerable current is induced iu the coils. This 
occurs after a very few turns, and it may be utilized in any 
way of a similar nature to that for which the ordinary cur- 
rent produced by a magneto-electrical machine is available, 
by simply discharging it through any circuit required. 

This property of soft iron was discovered by Dr. Werner 
Siemens, of Berlin. He states that there is always sufficient 
residual magnetism in the soft iron to induce a small current 
in the coils, and in these instruments the re-action of mag- 
netism on currents, and vice versa, increases this residual 
magnetism very rapidly. 
wffh e silme e rTs's One °f Sieniens's small instruments, weighing 28 pounds, 
mSe! electrical has been tried at the School of Military Engineering, 
at Chatham, with the following result: 

Twelve Abel's fuses, out of twenty, placed in continuous 
circuit in dry air, were exploded at the second discharge. 
Twelve Abel's fuses placed in divided circuit in dry air were 
fired, one at the first discharge and eleven at the second. The 
instrument is so arranged that several turns of the handle 
are made in the first instance on short circuit, in order to 
accumulate a sufficient charge in the coils, and on arrival 
at a certain point this accumulation is discharged through 
the main circuit in which the fuses to be fired are placed. 
In order to produce this latter result, the short circuit is 
broken by means of a cam in connection with, and turned 
by, the handle by which the armature is put in motion, 
which allows a spring to descend and simultaneously to 
break the short and complete the firing circuit. The reason 
of the partial failure in the two experiments mentioned was, 
that the handle had been turned very nearly up to the point 
wherethe action of the cam, throwing in the firing circuit, took 
place, and consequently, instead of the accumulated charge 
produced by several turns being stored up, only that due 
to one or two turns was discharged through the firing-circuit. 
It is necessary, therefore, in using this instrument, to 
commence turning the handle from that point where the 
maximum number of turns, before the discharge, is ob- 
tained. In subsequent experiments, where this precaution 
was taken, no failure of the nature described took place. It 
may be assumed, therefore, that the instrument in question 
possesses the power to fire twelve Abel's fuses, either in con- 
tinuous or divided circuit, in dry air. As the fuses are all 
fired by a single discharge, and not by a succession of short 
currents as in Wheat stone's magnetic exploder, the num- 
ber which may be relied on to be fired in earth, dry or 
damp, or in sea-water, depends upon the quality of the m- 



167 



sulation of the electric cable. To test this, a single Abel's 
fuse was fired with this instrument through a quarter of a 
mile of cable, (a strand of 7 No. 22 copper wires, insulated 
with Hooper's dielectric to a diameter of T 3 y inch ;) it 
failed to fire with a leak of ^ inch. With the same cable 
the ebonite frictional machine failed with a leak of J inch. 
With a conductor consisting of 1J miles of similar cable, 
the dynamo-electrical machine failed to fire the fuse with a 
leak of 3L inch. With the same cable the frictional ma- 
chine failed with a leak of J inch. As regards power to 
overcome a leak, therefore, a dynamo-electrical machine of 
this weight (28 J pounds) is about on a par with Wheatstone's 
exploder, weighing 31 pounds, which has been tried against 
it for the sake of comparison. 

Machines of this nature may be made of considerable 
size, and, where portability is not essential, may be ar- 
ranged to develop a very considerable electrical current. 

Mr. Ladd, of Beak street, London, has invented another Ladav* dynamo- 

' electrical machine. 

instrument adapted to the explosion of mines, the principle 
of which is precisely similar to that of Siemens's dynamo- 
electrical machine, but the arrangements differ, inasmuch 
as Ladd employs two armatures, one to create the electro- 
magnet, and the other to produce a current therefrom, with 
which to perform any w r ork required. Fig. 71 gives the 
general arrangements of the instrument; (a a) are two soft- 
iron bars, around which coils of fine insulated w 7 ire (b b) 

Fig. 71. 




are wound, in metallic connection, through a commutator, 
with the coil of an armature, (c,) revolving between their 
extremities. When the armature (c) is made to revolve, 
exactly the same effect is produced as in Siemens's instru- 
ment, and the result is that the two bars (a a) become 
very powerful electro magnets, the poles of which are so 
arranged as to be exposed to each other at their extremi- 
ties. Now, instead of discharging the current thus induced 
through his working-circuit, to fire fuses or perform any other 
work which necessitates the beginning again, as it were, to 



168 

create -a new current, Mr. Ladd introduces a second arma- 
ture, (d,) revolving between the soft iron bars, from which 
he obtains his working-current ; the magnetism of the bars 
is thus always kept up. The residual magnetism of the 
system is always sufficient to commence the action de- 
scribed, except, possibly, when an instrument had just been 
made, and had never been used, when it might be neces- 
sary to touch the bars with a permanent magnet, or pass a 
voltaic current through the coils for an instant, to obtain 
the magnetism required. An instrument of this nature was 
exhibited at the Paris Exhibition of 18G7; it was only 24 
inehes long, 12 inches broad, and 7 inches thick, but the ef- 
fects produced by it when worked by a steam-engine of one 
horse-power were very great, and would seem to augur 
well for the future of this system, which Mr. Ladd proposes 
to apply to the production of an electric light for light-house 
purposes, the principle is, of course, equally applicable to 
the ignition of charges of gunpowder or other explosives. 

The following description of another instrument of a sim- 
ilar nature is extracted from the report of the committee 
on active obstructions, page 86 : 
Magneto -ex- "A small magneto-electric exploding machine, which was 

ploder, by Mar- ° i » 7 

kus of Vienna. first devised by Herr Markus, an Austrian philosophical- 
instrument maker, at the suggestion of Baron Von Ebner, 
(after the latter had witnessed the performances of Wheat- 
stone's instruments and Abel's fuses in England in 1882,) 
and which is stated to be employed in the Prussian service, 
was obtained by government for the purposes of the com- 
mittee from Messrs. Gessler & Co., of Berlin. This instru- 
ment is not more than half the size of Wheatstone's explo- 
ders, from which it differs materially as regards the mode 
by which the generation of magneto-electric currents is 
effected. It was only disposed of to the English govern- 
ment upon the understanding that it was not to be exam- 
ined, and no detailed description of its construction can, 
therefore, be attempted, but the mode of using it affords a 
sufficient indication of the manner in which the magneto- 
electric current is generated. The magneto-electric ap- 
paratus is completely inclosed in a square oblong metal 
case, to one side of which are fixed two binding-screws, 
(a a,) Fig. 72, for connecting the instrument with the 
conducting-wires, while one of the ends forming the top 
of the case carries the arrangement for 'setting' the instru- 
ment and firing the mine. 
Mode of using » Before this magnetic exploder is connected with the 

the instrument. -,,. . , .,, .-.-, ,-, ^ ~ -, 

conductmg-wires, a key, with powerful leverage, (&,) fixed 
upon the top of the instrument, to which it always serves 




169 

as a handle, is turned to the right as far as possible. By 
this operation the armature of the inclosed magneto-elee- 
Fig. 72 tric ma( ' nilie is separated from the magnet 
and placed under the influence of a power- 
ful spring. This spring is in connection with 
a pin (c) which projects from the top of the 
instrument, and moves as the key is turned 
in a slot of a long spring, (d,) one end of 
which is fixed upon the instrument, while 
the other carries a knob made of ebonite, 
(e.) When the key has been turned to the 
full extent, the pin which controls the ar- 
mature spring has become firmly fixed by its 
head in the slot of the external spring, (d,) and the instru- 
ment is now ready for action at any moment. It is then 
connected with both conducting- wires, and the explosion 
of the charge is accomplished by pressing down the ebon- 
ite knob, (e,) whereupon the armature spring is released by 
the liberation of the pin (c) from the outer spring (t?,) and 
the armature returns to the magnet with great velocity, an 
electric current being thereby established. 

"This instrument is even more portable than Wheatstone's 
ordinary exploder, and is fully as powerful — i. e. it is ca- 
pable of exploding as many, if not more, charges in simple 
circuit; but it is much more limited in its power of firing 
charges through a divided circuit, because it is incapable of 
furnishing a succession of currents, such as obtained by 
means of YTheatstone's and Beardslee's instruments. 

" Several of these instruments of different size and power, 
constructed by Markus, were exhibited among the collection 
of military implements sent to the recent Paris Exhibition 
by the Austrian government. The smallest of the machines 
was stated to be capable of exploding live or six of Yon 
Ebner's fuses, and the largest fifteeen in simple circuit. That 
officer states that the magneto-electric instruments of 
Markus have been introduced into the Austrian service for 
land operations in place of the frictional electrical machine. 
" Some very efficient rotary magnetic exploders, similar 
in their powers to Wheatstone's ordinary exploders, and 
differing only from them in details of construction, were 
also shown in the exhibition of the Austrian war department 
at Paris." 

Fuses adapted to electricity of high tension, may also be 
fired by means of the induction-coil, for which they must be 
connected in simple divided circuit, for the same reason that 
it is necessary so to arrange them for Wheatstone's mag- 



Indiictiou-coi 



170 

netic exploder, viz, that the action produced is a very rapid 
succession of currents of very short duration. 

The defects of all these instruments for submarine mining 
purposes are the same as those of Wheatstone's magnetic 
exploder, viz, the small quantity of the current, which ren- 
ders it necessary to employ a cable with very perfect insula- 
tion. 
Pnctionai eiec- Next, as regards the use of frictional electricity as an ex- 

trical machines. ' 

plocling agent for submarine mines. The well-known fric- 
tional machine, designed by Baron Yon Ebner, colonel of 
the Austrian corps of engineers, is a very good type of in- 
struments of this class. Several instruments of this kind, 
but slightly differing in size and construction, were exhibited 
at Paris in 1867 by the Austrian war department. Some of 
them were made with glass disks and inclosed in a wooden 
box, but the best for military purposes are those in which 
the glass disks are replaced by ebonite, as described in the 
Course of Instruction in Military Engineering, page 156, par. 
334. 

These instruments produce a charge of electricity much 
larger in quantity and higher in tension than either the 
magneto-induction or dynamo-electrical machines. One of 
their defects is the time required to charge the condenser,, 
which takes from 20 to 30 seconds, and the condenser must 
be recharged after each explosion. There is also a certain 
liability for the charge to leak out of the condenser when 
the air is highly charged with moisture, but when the instru- 
ment is in good working order and Abel's fuse may be fired 
with it through a considerable resistance, say 13 B. A. units, 
on a mile of No. 16 copper wire, from 15 to 20 minutes after 
the condenser has been charged, and under favorable cir- 
cumstances we have fired one after an interval of 6 hours. 

The chief defect of this instrument is the danger, when 
using it, of accidental ignition to mines, the con ducting- 
cables of which may be in the vicinity of that in connection 
with the mine to be fired, as shown by the experiments de- 
tailed in page 121. Some further experiments have since 
been made at the School of Military Engineering, Chatham, 
to ascertain the limits within which the inductive action is 
so energetic as to render it dangerous to lay electric cables, 
when mines are to be fired by means of frictional and induced 
electricity. From these it is evident that the utmost care is 
necessary in using the frictional machine. 

On the 18th of May, 1870, two half-miles of electric cable, 

• each consisting of a strand of 7 No. 20 copper wires, insulated 

to a diameter of j^-inch with Hooper's patent dielectric, were 



171 

laid out and connected with fuses. The fuses were placed 
20 yards apart, and the line was, in each case, put to earth 
beyond them. One of the cables was connected with the 
instrument used for firing the fuse, the end of the other, at 
the point from whence the fuses were fired, being carefully 
insulated. The two cables were laid parallel to each other 
as far as they would go, till it becomes necessary to diverge 
to the positions where the fuses were to be placed; they 
therefore lay under conditions favourable for inductive action 
for nearly half a mile. The annexed table, page 1G0, gives 
the results obtained : 

Tabic of experiments to ascertain the limits within which the inductive action 
of frictional electricity is sufficient to fire an AbeVs fuse under the condi- 
tions specified. 



6 feet 
3 feet 
3 feet 

9 feet 
12 feet 

15 feet 

15 feet 
15 feet 
20 feet 

20 feet 
30 feet 
40 feet 

40 feet 
40 feet 
40 feet 
35 feet 
30 feet 



Instrument used. 



Touching 

Touching 
Touching 

Touching 



Frictional. 

do... 

do ... 



goo 



3 £Jj+3 



Dynamo - electric 
machine. 

do 

Wheatstone's mag- 
netic exploder. 

do 



Results. 



Both fuses fired ; one directly, one hy induction. 

Do. 
One fuse fired on direct circuit, second fuse 

not fired by induction. 
Both fuses fired; one directly, one by induction. 

Do. 
One fuse fired on direct circuit, second fuse 
not fired by induction. 
Do. 
Both fuses fired; one directly, one by induction . 
One fuse fired on direct circuit, second fuse 

not fired by induction. 
Both fuses fired; one directly, one by induction. 

Do. 
One fuse fired on direct circuit, second fuse 
not fired by induction. 
Do. 
Do. 
*Do. 
Do. 
Both fuses fired ; one on direct circuit, one by 

induction. 
One fuse fired on direct circuit, second fuse 
not fired by induction. 
Do. 
Do. 



Do. 



* The second fuse was changed in this case, in order to ascertain that the failure 
to fire did not arise from a defective fuse, or one comparatively less sensitive. 

From this it is evident that the use of frictional electricity, Frictional eiec- 

,.•.,. - . . ,. . .. tricity only appli- 

in connection with a system of submarine mines, is limited cable to excep- 

, -• i -r-i • i • i? tional cases. 

to very exceptional cases. For certain purposes, as, for 



172 

example, with isolated mines, this instrument is no doubt a 
valuable agent, but in consequence of the great danger, 
inseparable from the inductive effect of the discharge, to 
which it is subject, it should only be intrusted to careful 
men who are thoroughly acquainted with its use. 
ei^tricaimachTne Takin g intoconsi deration the advantages and defects of 
seems to be the eac h f tlie instruments described, it would seem that the 

best for general 7 

use - dynamo electrical machine is the best adapted for use in 

connection with a system of submarine mines. When made of 
moderate size it is sufficiently portable for all practical pur- 
poses, while at the same time its power to generate a charge 
of electricity renders it available, under nearly all conditions, 
for the ignition of a mine with certainty. The absence of 
permanent magnets gives it an advantage over Wheatstone's 
magnetic exploder and Markus's machine, and there is, with 
the smaller form of instrument, no danger of explosion by 
induction, as in the case of the friction al machine. This 
latter should never be used where any other electrical ignit- 
ing agent is obtainable. 

tery^ow^r. y a " We now come to the ignition of submarine mines by bat- 
tery-power. For use in connection with forts, or in stationary 
positions, there is no doubt that the battery is by far the 
most important agent. 

Battery lor use 

with platinum Where a platinum- wire iuse is used, a current of large 
quantity is necessary to insure ignition. For this purpose 
Grove's, or Walker's, or some battery producing electricity 
of the requisite nature, must be used. This question has 
already been discussed. See page 93 and those following. 

Groves battery. A description of Grove's battery, with the general principles 
to be borne in mind in using it, is given at page 138, par. 295 
of The Course of Instruction in Military Engineering, and the 
paragraphs following. 

walker's zinc- A platinum wire fuse may be used in connection with 
cm-bon battery. Walker's constant battery. Some experiments have been 
tried at the School of Military Engineering, at Chatham, 
with this form of battery. 

Experiments. The battery was composed of two cylinders of zinc, each 
T 3 g inch thick, 7 inches long, and 3 inches in diameter, con- 
nected together so as to form a single metallic plate, and two 
cylinders of graphite, each § inch thick, 7 inches long, and 3 
inches in diameter, similarly connected. The cells were 
formed of gutta-percha pots, 7J inches in diameter and 7 
inches deep, capable of containing about half a gallon of 
liquid. If the battery-plates had been made in one single 
piece, instead of in two portions, the whole would have been 
very much more compact, but at the time it was made the 



173 

manufacturers had no large plates in stock, and those de- 
scribed above were used to save time. 

The battery was made upon theVtOth of December, 1809. 
The number of cells employed was four, and r 3 () inch of pla- 
tinum wire, weighing 1.6 grains to the yard, was employed, 
as the standard of measure to ascertain the fusing-power 
of the current. The electrical resistance of one turn of the 
rheostat employed was .02-19 B. A. unit. The proportion 
of acid to water used in the cells was one of acid to ten of 
water. 

December 10, 18G9. — Platinum wire fused through 21 turns 
on rheostat. 

December 13, 18G9. — Platinum wire fused through 19 turns 
on rheostat. 

December 17, 18G9. — Platinum wire fused through 28 turns 
on rheostat. 

December 20, 18G9. — Platinum wire fused through 31 turns 
on rheostat. 

December 23, 1869.— Platinum wire fused through 25 turns 
on rheostat. 

December 30, 1869. — Platinum wire fused through 26 turns 
on rheostat. 

December 31, 18G9. — Platinum wire fused through 28 turns 
on rheostat. 

January 3, 1870. — Platinum wire fused through 30 turns 
on rheostat. 

January 1, 1870. — Platinum wire fused through 30 turns 
on rheostat. ; 

January 5, 1870. — Platinum wire fused through 30 turns 
on rheostat. 

January G, 1870. — Platinum wire fused through 32 turns 
on rheostat. 

January 7, 1870. — Platinum wire fused through 32 turns 
on rheostat. 

January 10, 1870. — Platinum wire fused through 30 turns 
on rheostat. 

January 12, 1870. — Platinum wire fused through 30 turns 
on rheostat. 

January 14, 1870. — Platinum wire fused through 29 turns 
on rheostat. 

January 15, 1870. — Platinum wire fused through 28 turns 
on rheostat. 

January 17, 1870 — Platinum wire fused through 30 turns 
on rheostat. 

January 19, 1870. — Platinum wire fused through 30 turns 
on rheostat. 



174 

January 24, 1870.— Platinum wire fused through 26 turns 
on rheostat. 

January 25, 1870. — Platinum wire fused through 26 turns 
on rheostat. 

January 2G, 1870. — Platinum wire fused through 24 turns 
on rheostat. 

January 28, 1870. — Platinum wire fused through 23 turns 
on rheostat. 

January 29, 1870. — Platinum wire fused through 23 turns 
on rheostat. 

January 31, 1870. — Platinum wire fused through 25 turns 
on rheostat. 

February 1, 1870. — Platinum wire fused through 25 turns 
on rheostat. 

February 2, 1870. — Platinum wire fused through 23 turns 
on rheostat. 

February 3, 1870. — Platinum wire fused through 24 turns 
on rheostat. 

February 4, 1870. — Platinum wire fused through 24 turns 
on rheostat. 

February 6, 1870. — Platinum wire fused through 24 turns 
on rheostat. 

February 8, 1870. — Platinum wire fused through 24 turns 
on rheostat. 

February 9, 1870. — Platinum wire fused through 24 turns 
on rheostat. 

February 10, 1870. — Platinum wire fused through 23 turns 
on rheostat. 

February 11, 1870. — Platinum wire fused through 22 turns 
on rheostat. 

February 12,* 1870. — Platinum wire fused through 18 turns 
on rheostat. 

February 14, 1870. — Platinum wire fused through L9 turns 
on rheostat. 

February 15, 1870. — Platinum wire fused through 20 turns 
on rheostat. 

February 17, 1870. — Platinum wire fused through 20 turns 
on rheostat. 

February 18, 1870. — Platinum wire fused through 20 turns 
on rheostat- 
February 21, 1870. — Platinum wire fused through 20 turns 
on rheostat. 

February 22, 1870. — Platinum wire fused through 19 turns 
on rheostat. 

* On this day the battery was removed from one table to another. 



175 

February 23, 1S70. — Platinum wire fused through 19 turns 
on rheostat. 

February 24, 1870. — Platinum wire fused through 18 turns 
on rheostat. 

February 25, 1870. — Platinum wire fused through 18 turns 
on rheostat. 

•The battery was made up afresh on the 25th February, 
with fresh acid and water, (1 acid to 10 of water,) and zinc 
plates re- a m alga mated. At the first test, made five minutes 
after filling the cells, y^- inch platinum wire wasfused through 
32 turns of the rheostat. The experiments were continued 
as follows : 

February 20, 1870. — Platinum wire fused through 32 turns 
on rheostot. 

February 28, 1870. — Platinum wire fused through 33 turns 
on rheostat. 

March 1, 1870. — Platinum wire fused through 33 turns 
on rheostat. 

March 2, 1870. — Platinum wire fused through 34 turns 
on rheostat. 

March 3, 1870. — Platinum wire fused through 34 turns 
on rheostat. 

March 4, 1870. — Platinum wire fused through 34 turns 
on rheostat. 

March 5, 1870. — Platinum wire fused through 35 turns 
on rheostat. 

March 7, 1870. — Platinum wire fused through 35 turns 
on rheostat. 

March 8, 1870. — Platinum wire fused through 34 turns 
on rheostat. 

March 9, 1870. — Platinum wire fused through 34 turns 
on rheostat. 

March 11, 1870. — Platinum wire fused through 32 turns 
on rheostat. 

March 14, 1870. — Platinum wire fused through 32 turns 
on rheostat. 

March 16, 1870. — Platinum wire fused through 32 turns 
on rheostat. 

March 20, 1870. — Platinum wire fused through 30 turns 
on rheostat. 

March 22, 1870. — Platinum wire fused through 30 turns 
on rheostat. 

March 25, 1870.— Platinum wire fused through 28 turns 
on rheostat. 

March 28, 1870. — Platinum wire fused through 28 turns 
on rheostat. 



176 

March 29, 1870.— Platinum wire fused through 27 turns 
on rheostat. 

March 31, 1870. — Platinum wire fused through 25 turns 
on rheostat. 

April 3, 1870. — Platinum wire fused through 23 turns on 
rheostat. 

April 5, 1870. — Platinum wire fused through 23 turns on 
rheostat. 

April 8, 1870. — Platinum wire fused through 21 turns on 
rheostat. 

April 10, 1870. — Platinum wire fused through 20 turns 
on rheostat. 

April 11, 1870. — Platinum wire fused through 20 turns 
on rheostat. 

April 13, 1870. — Platinum wire fused through 19 turns 
on rheostat. 
Battery proved The results obtained have proved this battery to be very ' 

very constant. " * 

constant, so that there need be no further doubt on that 
account as to the use of the platinum-wire fuse. The want 
of constancy in Grove's battery is certainly a serious con- 
sideration. It will be observed that on the 12th of Febru- 
ary, when the battery was moved from one table to another 
ii\ the same room, there was a slight depreciation in the 
fusing- power of the current, but that it subsequently, to a 
certain extent, recovered itself. It should therefore be moved 
as little as possible, but as it is only applicable to perma- 
nent stations, this is not of much consequence. It was 
noticed, too, that if the circuit was kept closed, that is to 
say, a constant flow of current kept up, its working 
power was materially diminished, as shown by the smaller 
number of turns through which the plantinum wire was 
fused. As, however, in any system of submarine mines, 
the circuit would only be closed for an instant, as each 
mine was fired, and as no continuous work would be required, 
this latter, though a fact to be noticed, need not interfere 
with its use for such a purpose. The cost of a cell of a bat- 
tery of this form would be comparatively large, but, on the 
other hand, a much smaller number of cells would do the 
work. Its size and weight are ill-adapted to portability, 
but for a permanent station this is of comparatively little 
consequence. 

Experiments with a much larger number of cells must be 
made before any definite conclusion, as to the -advantage of 
this form of battery, can be arrived at. As far as we have 
yet gone, however, it promises remarkably well. 



177 
To fire a fuse adapted to electricity of tension, such as Battery for use 

.,,,,. t ,. ,-, t /• n i with tension-fuse. 

Abel's for example, any ot the ordinary forms of battery 
used for working a line of electric telegraph may be employed ; 
the object in such a case being to obtain electro-motive force 
rather than quantity. It is of importance that the battery 
should be constant — that is to say, that it should be capable 
of being allowed to remain mounted and ready for use for 
a considerable time, say a month, and not, like Grove's, re- 
quired to be taken to pieces and refitted every twelve hours ; 
that it should generate a sufficient quantity of electricity to 
allow of a certain amount of leak or fault in a cable and yet 
tire a fuse beyond that leak; and, at the same time, that 
the electro motive force to be obtained from the battery may 
be such as, with a sufficient number of cells, to fire an Abel's 
fuse with certainty. 

The best forms of battery for this purpose seem to be 
Wollaston's sand-battery, the Marie-Davy battery, andDan- 
ielFs battery. 

The ord inary form of san d-battery is shown in Fig. 73, twelve waiiasnn - i 

battery. 

Fig. 73. • 



cells being united in a trough made of gutta-percha. The usual 
dimensions of the plates are 3J by 4J inches. They are 
alternately copper and zinc, connected together in pairs by 
copper strips riveted and soldered to them. The zinc plates 
are amalgamated with mercury, and the cells are filled with 
fine siliceous sand, moistened with sulphuric acid diluted with 
water in the proportion of T V. This battery develops a 
powerful current of electricity when first made up, but, when 
the circuit is kept constantly closed, it is very incon- 
stant, and after being in use for a certain time, varying 
according to circumstances, it loses its power from various 
causes ; the sand must then be washed out, and the battery 
made up again with fresh solution and the zincs re-amalga- 
mated. 

12 



Defects 



mprovements, 



178 

The great defect of the simple combination of zinc and 
copper in dilute acid is, that the bubbles of hydrogen-gas 
resulting from the decomposition of the water by the electric 
force adhere to the copper plate, and, being in a state of 
electrical polarization, act in opposition to the direct current 
and reduce its strength very materially; moreover, the 
hydrogen being in what is termed the nascent state, com- 
bines very readily with the oxygen of the sulphate of zinc, 
produced by the action of the battery, and metallic zinc is 
thus deposited upon the copper plates, and so, similar metals 
being opposed to each other, the action of the battery ceases. 
Many methods have been adopted to get rid of the hydrogen. 
In Grove's and DanielFs batteries it combines with the 
oxygen of the solution in which the electro-negative metal 
is immersed. In Smee's, and its kindred forms of battery, 
the hydrogen is assisted in escaping from the negative plate 
by giving it a rough surface, presenting a multitude of small 
points from which the bubbles separate easily. 

The sand is chiefly useful to prevent the acid from spilling 
when the battery is moved about; it tends also to make the 
action of the battery more regular; but it should not contain 
carbonates, such as carbonate of lime, or a chemical action 
takes place with the sulphuric acid, which is detrimental to 
the battery. 

In the best form of this battery a small gutta-percha pipe 
is inserted in each cell, extending down to the bottom ; 
through this fresh diluted acid is poured in from time to 
time to make up for waste by evaporation. By thus intro- 
ducing the fresh acid at the bottom of the cell, where the 
heavy sulphate of zinc gravitates, a more regular action is 
obtained. If the sulphate of zinc be allowed to accumulate 
in the lower part of the cell, a cross voltaic current is estab- 
lished between the upper and lower portions of the plates 
which are in solutions of different strengths. The effective 
current in circulation is thus diminished, and the upper 
portion of the zinc plates are rapidly dissolved away. 

lbs. oz. 

The weight of the 12-cell battery is, without sand 

or liquid . . 14 14 

With sand 22 00 

Sand and liquid 23 12J 

It requires about 1 pound of mercury and two pints of acid 
per annum for each 12 cells. 

For submarine mining purposes the conditions are different 
from those which occur in the simple working of a line of 
electric telegraph, in which the circuit would be closed much 



179 

more frequently and for longer periods ; under these latter 
circumstances its defects become much more apparent, as 
the mischief is done almost entirely when the circuit is closed. 
This fact, however, reuders it less objectionable as a firing 
agent for submarine mines than as a battery for telegraphic 
purposes. 

A solution of sulphate of zinc is sometimes used, as an 
exciting fluid, instead of diluted sulphuric acid; the effect 
under such circumstances is, to a certain extent, to reduce 
the consumption of zinc, with a reduction, however, of the 
active force of the current generated. A battery of this form, 
charged with diluted sulphuric acid, is more energetic when 
first made up, while one charged with sulphate of zinc is, 
after coming fairly into a working state, more constant and 
requires less attention to keep it in good order. One advan- 
tage of sulphate of zinc is that, being in the form of crystals, 
it can be more easily stored and carried about than sulphuric 
acid; this is a very decided advantage or board ship. 

This battery possesses another advantage for use on board 
ship, inasmuch as the liquid being kept absorbed in the sand 
is not liable to be split. 

There are several forms of the Marie-Davy battery which Marie-Davy bar - 
might be used for firing Abel's fuses; it may be described ery ' 
as consisting generally of plates of zinc, and carbon in a 
saturated solution ofproto-sulphate of mercury. 

One form of this battery, called " Silver's Marine Battery ," 
has been manufactured by the India-rubber, Gutta-percha, 
and Telegraph-works Company, of Xorth Woolwich, ex- 
pressly for use with Gisborne's system for signaling on 
board ship ; it consists of a combination of zinc and plat- 
inized graphite plates in a saturated solution of proto-sul- 
phate of mercury. This is perhaps the best and most constant 
form of battery of this nature, but it is rather bulky. It could 
be used on board ship, having been expressly manufactured 
for sea service, to stand rolling about. The smaller forms 
of the Marie-Davy battery, which have been tried in the 
electrical school at Chatham, though excellent when first 
made up, both as regards quantity and electro-motive force, 
deteriorate very rapidly, and are not so good for submarine 
mining purposes as Daniell's form. 

Daniell's constant battery is well known to all persons Danieiis con- 
engaged in working the electric telegraph, and consists of staDt battery - 
zinc and copper elements in a saturated solution of sulphate 
of copper. The copper plate is placed in a porous cell with 
a quantity of sulphate of copper in the form of crystals., and 
water is poured in, which dissolves the latter and sets up an 



180 



electrical action. An excess of sulphate of copper must be 
placed iu the porous cell to keep the solution, as it is termed, 
saturated, or, iu other words, carrying a maximum of the 
sulphate of copper in solution. 
Muirhead'sform Muirhead's form of Daniell's battery would be a very ffood 

of Darnells bat- "- J ° 

f ery. one for stationary submarine service. It consists of the 

usual Daniell's elements, zinc and copper plates, the copper 
is a porous cell, the exciting liquid being a saturated solu- 
tion of sulphate of copper. The plates in this form of bat- 
tery are comparatively large, which is advantageous when 
a defect exists in an electrical cable. The greater the im- 
mersed surface of the plates, the greater the quantity of the 
current generated. 
Variey'sform of Another form of Daniell's battery, suitable for use with 

Darnell s battery. " ' 

Abel's or any similarly constituted fuse, is Varley's. The 
arrangement proposed is shown in section, Fig. 74; (a) is 
the outer cell, of cylindrical form, and 
made of common glazed earthenware; 
(b) is the zinc element, a semi-cylin- 
der, of thick cast zinc, occupying the 
upper half of the outer cell, and with a 
m etal strip to connect it with the copper 
plate of the adjoining cell ; (c) is the (Z 
copper element, occupying the lower 
half of the cell, and consisting of a 
thm plate of copper wound round and 
round, so as to expose a sufficient 
metallic surface ; the connection with 
the zinc plate of the adjoining cell consists of a copper strip 
passing up through a glazed earthenware cylinder, (d ;) (e) 
is a porous diaphragm consisting of several thicknesses of 
flannel, fitting tightly round the glazed cylinder (d) and 
completely filling up the space between it and the outer cell 
(a.) This flannel diaphragm is the chief peculiarity of this 
form of battery ; it supplies the place of the porous cell in 
the other combinations of Daniell, and is so placed that, 
taking advantage of the greater specific gravity of a solu- 
tion of sulphate of copper over a solution of sulphate of 
zinc, each metal may be, to a great extent, in a solution of 
its own sulphate ; that is to say, the copper in a solution of 
sulphate of copper, the zinc in a solution of sulphate of zinc. 
To set the battery in action, crystals of sulphate of copper 
are dropped through the glazed cylinder (d) into the lower 
portion of the cell, and water is then poured in. When first 
put together this battery does not at once produce a maxi- 
mum of working current ; it gradually improves for the first 




181 

forty-eight Lours, after which it remains very constant for 
a long period. TLe flannel diaphragm produces a LigL in- 
ternal resistance in tLe cell, but, taking it on tLe wLole, it 
seems to be one of tLe most efficient batteries for subma- 
rine-mining purposes, for which service its constancy, when 
once fairly in action, is a very desirable quality. 

A battery in connection with the torpedoes exLibited by , Austrian battery 

«- *■ " tor suomanin- 

the Austrian government at Paris in 1867 is also worthy of ™°es. 
notice. It was designed by Baron Yon Ebner, colonel of 
the Austrian imperial corps of engineers, and is described 
as follows, in tLe notices of objects exLibited by the Aus- 
trian war department : 

" These batteries may be considered a modification of tbat 
known as Sinee's. 

•'TLe large quantity of liquid contained in tLe cell retards 
considerably tLe tendency to alter its internal resistance : 
platinized lead is used instead of platinized silver for tLe 
positive pole of tLe battery ; and zinc, cut up into pieces 
and held in a bath of mercury — tLe wLole in a porcelain 
cup, pierced so as to admit tLe diluted acid freely — forms 
tLe negative pole of tLe battery. 

"The consumption of zinc and mercury, wbicL is very 
considerable in tLe ordinary battery, is thus materially 
diminished. 

"These batteries have been employed for sometime in 
working a system of telegraph instruments of dial form. 
In this case the force of the electric current required is very 
small, but so little zinc was consumed that the batteries 
worked for eighteen months without being touched. 77 
The general form of one of these cells is shown in Fig. 75. 
It consists of a vessel of glass (a) 
18 inches deep and 5 inches in 
diameter, to contain the diluted 
sulphuric acid, within which is 
suspended a plate (b) of platin- 
ized lead, which is bent round 
into a cylindrical form to fit close 
around the inner surface of the 
glass. In the center of this lat- 
ter is hung the porcelain perfor- 
ated cup [containing the cut-up 
zinc and mercury, to keep it (the zinc) amalgamated. This 
is shown in elevation at (c) and in section at (d.) 

The top of each cell is furnished with a porcelain cover, 
through which the wires attached to the positive and nega- 
tive plates pass for convenience of connection. The cells 
are arranged in a wooden frame in batteries of twelve each. 




182 




This battery is said to be very constant, but its great 
bulk is much against it. 
^Lecianch6 bat- Iu tlie French section of the Paris Exhibition of 1867, a 
form of battery, invented by M. Leclanche, and manufactured 
by Messrs. Bonner, Jamin, Bailly & Co., Paris, was shown. 
Fig. 76 represents a cell of this battery. The positive pole 
(a) consists of a plate of graphite in jv^. 7g # 

a porous jar surrounded by a mix- 
ture of peroxide of manganese and j\ 
graphite broken up into small pieces. ® 
The negative pole (b) is a plate or 
pencil of amalgamated zinc. The 
whole is in an outer glass cell (c) 
containing a solution of sal-ammo- 
niac. The peroxide of manganese is 
a good conductor of electricity. This 
system may be described as a bat- 
tery with one acid, and of which 
the positive pole has great affinity 
for hydrogen. 

The endosmosis, inevitable in a battery of two acids, is 
avoided in this combination. Zinc may be preserved for a 
long period in a solution of sal-ammoniac, and peroxide of 
manganese being quite insoluble in that liquid, local chemi- 
cal action is avoided. When the circuit of the battery is 
closed, the hydrochlorate of ammonia is decomposed, and 
chloride of zinc is formed. The electro- motive force of this 
battery is said to be considerable, 28 elements of the Le- 
clanche battery being said to be equal to 40 of Daniell's. 
Its internal (or liquid) resistance is also said to be very small. 

It has been adopted by the chemius de fer de l'Est, de 
FOuest, du Eord, de Paris, and Lyons a la Mediterranee, and 
in the former is said to have been tried for ten months 
with very excellent results. 

The advantages claimed for it are, absence of chemical 
action when the battery circuit is not complete, and con- 
sequently no waste of material ; it requires little or no look- 
ing after $ the cost of maintenance is small; it cannot be 
injured by mixing or upsetting the liquids ; the battery, 
ready for action, may be placed in store without deteriora- 
tion or loss in its component parts; and it possesses great 
facility for transport, without injury to the working powers. 

This battery seems to possess qualities which may ren- 
der it useful as an agent for submarine mining purposes, 
and experiments should be made with it in order to ascer- 
tain its advantages for this purpose. 



183 

For boat service, a voltaic pile has been devised by F. voltaic pile. 
Abel, esq., F. R. S. It is described as follows in the report 
of the committee on active obstructions : 

" This batter y-cousists of a series of pairs of zinc and copper *? x . te ™ p orized 

'' •"- A L voltaic pile. 

disks, or square plates, each pair being separated by a piece 
of flannel ot corresponding size, steeped in a saturated 
solution of salfc acidified with a little vinegar, the pairs being 
arranged in four x^iles, connected by strips of metal with 
each other, and confined between two boards in such a man- 
ner that they afford the means of pressing the disks com- 
pactly together. The most efficient form of this battery is 
constructed as follows : 

il A piece of hard, dry wood, (a,) Fig. 77, about 7£ inches construction. 
square and 1 inch thick, is well lacquered or varnished on 
its upper surface, or coated with a mixture of gutta-percha 
and pitch, or of bees- wax, rosin, and pitch. A wooden rod," 
2 of an inch in diameter and 11 inches in height, with a 
screw cut upon about 6 inches of its upper end, is fixed 
vertically into the center of the wooden slab. 

"Around this rod are arranged four piles of zinc and cop- 
per plates, (c c,) either square or circular, of 2J to 2| inches 
diameter, and which may be cut out of smooth copper 
and zinc sheets. Eight slight wooden rods or sticks, (e e,) 9 
inches in height and about J of an inch in thickness, are 
loosely fixed into perforations in the board so as to be capa- 
ble of removal at pleasure, being merely required to support 
the metal plates during the process of piling them. 

" The two poles of the battery (//) are formed of two 
strips of copper about J of an inch in width, and of suffi- 
cient length to reach from the. exterior of the board to the 
center of one of the piles of plates. One end of each strip 
of copper is bent downward and fixed into a separate small 
slot cut into the board near one edge. 

"A number of disks of flannel are prepared J of an inch 
less in diameter than the metal plates. They may consist 
of old blanket or of a double thickness of service cartridge 
serge roughly stitched together." 

The mode of arranging the battery is as follows : Arrangement for 

u The flannel disks are soaked in a liquid prepared by ' 
saturating water with common salt, and adding some vinegar 
in the proportion of one ounce to a quart of water; they 
are afterward squeezed out as dry as possible by the hand 
before being used. A zinc plate is then placed upon one of " 
the strips of copper which lies flat on the board and leads 
into one of the slots, and a disk of flannel moistened as de- 
scribed is placed upon the zinc. A pair of copper and zinc 



Employment. 



Directions 
eaning it. 



184 

plates is then placed upon the flannel, the copper being- 
undermost ; a second flannel disk follows, then a pair of 
plates as before, and so on till a pile of 30 zinc, 30 flannel, 
and 30 copper disks has been completed. A precisely sim- 
ilar pile is then constructed by its side, the first plate being, 
however, copper in this instance, and the position of the 
copper and zinc disks in each pair being the opposite of that 
in the first pile, the zinc being, therefore, the lower plate. 
The top disk of pile No. 1, (copper,) and the top disk of pile 
No. 2, (zinc,) are then connected by laying a thin strip of 
copper (g) across them. The third pile is now commenced, 
a thin strip of copper (h) having been laid upon the board 
to connect it with the second pile. A zinc plate is taken 
first, this time as in the case of pile No. 1. Lastly, a fourth 
pile is commenced by placing a copper plate upon the strips 
of copper, which constitutes the second pole of the battery, 
and this pile is built up like No. 2 pile. The top disks of 
piles Nos. 3 and 4 are then connected by a strip of copper, (■*.) 

"A piece of hard wood, (7c,) similar to the bottom board, 
is well coated with pitch composition or varnish on one side, 
and is provided with a central perforation through which 
the screw is to pass, and with holes of sufficient size to 
allow all the thin rods which support the piles of plates to 
pass freely through. This board is placed with its coated 
side downward upon the piles, and is then pressed upon 
them by means of wooden nuts, (I £,) which are screwed on 
to the central rod. The plates are thus firmly held in their 
places, but the pressure applied by means of the screw must 
not be sufficiently great to squeeze any water out of the 
flannel disks. 

" If there is no workman or lathe at hand to provide the 
screw and nuts, the pile may be firmly braced together by 
passing two or three turns of stout cord round the boards 
and tightening these cord bands by means of wooden wedges. 

" To connect the battery with the firing-wires, the cleaned 
end of the conducting-wire is inserted into one of the slots 
containing a pole of the battery, and it is maintained in 
close contact with the copper strip in that slot by passing 
a wire round a small wooden wedge, which is then forced into 
the slot at (n.) The circuit is completed when required by 
bringing the return firing-wire (or earth-wire) into contact 
with the strip of copper forming the other pole of the bat- 
tery, (n\) 

r " When the battery is taken to pieces the flannels should 
be placed in water acidulated with vinegar or oil of vitriol, 
and, after having soaked for about one hour, they should be 



185 



washed in pure water and wrung out. The plates of zinc and 
copper should be thoroughly cleaned by scrubbing the in 
with wet sand." 

The working-force of the current of any voltaic battery o^Juf ry™- 
or pile is much improved when it (the battery) stands on a f.™ vod l) y insula - 
good insulating substance. When practicable, therefore, it 
is recommended that the whole battery or pile may be ar- 
ranged to stand upon a sheet of thick crown-glass. The 
reason of the improvement is, that the insulating substance 
prevents minutely small losses of current, which occur more 
or less in practice, even when batteries have been put to- 
gether with the utmost care, and which pass to earth with- 
out completing the working circuit when the battery stands 
upon any less perfectly insulating material. 

The following table gives the internal resistance and com- 
parative electro-motive force of several forms of voltaic 
battery: 





Size of plates. 


§1 

03 . 

g w 

l! 

is 


a . 

o 


Xame of battery. 


Copper or graph- 


Zinc. 


p * 

2 1 

o 




22" X 2" spiral . . 

U" X 4" 

4"Xf" 

3i"X4i" 

6»X1| 

lh" X If" 


5"X1|" 

3£" X4" 

3-1" X!" 


10 

7 

10 

15 

3 

2 


yii 


Mum-head's Daniell 


830 
858 


Wallaston's sand 


3i"X4i" 

6" long, I" diameter. . . 
6" loiig, 5-16" diameter. 


835 
1220 


Leclanche 


1065 



Xote.— These results have been obtained from cells freshly made tip ; the experi- 
ments were tried at 6 hours. 30 hours and 54 hours after the batteries were put together. 



CHAPTER XI. 

CLOSING ELECTBICAL, CIRCUIT. 

Having got our mines placed in position, established the 
conducting-cables to connect them with our testing-room, 
and selected the most approved form of "battery or igniting 
agent, it now becomes necessary to discuss how any par- 
ticular charge of a group may be fired at the right moment. 
This may be done at will, the position of the ship being 
determined by intersection, or the vessel herself may be 
made to complete the circuit by striking a circuit-closer. 
Firing by cross- In firing at will, the vessel's position beiog determined bv 

bearings or inter- 

section. intersection, several expedients may be adopted. 

The most simple is that in which an observer can be placed 
on the prolongation of a line of mines, as at (a,) Fig. 78, 



Fi 9 . 78. 




commanding the mines (m h m 2 , &c,) and on the prolongation 
of their direction a second observer being stationed at the 
point (b ;) {c z) represents the firing-battery, having one of 



187 

its poles (z) connected to the earth at (<?,) the other pole 
being attached to one point of contact of a tiring-key at (a.) 
From the pivot-point of the key an insulated cable, in con- 
nection therewith, passes to the pivot-points of a series of 
keys at (b.) Till the key at (a) is pressed down, no current 
can pass from the battery (c z) past the station (a,) but 
directly it is pressed down, the circuit is so far completed, 
and the line is charged up to the station (b.) From the 
station (b) a series of electrical cables, (b m h b m 2 , &&,) 
attached to a series of contact-points, perfectly distinct and 
carefully insulated from each other, passes to the mines (mi, 
m>, &c.,) through the fuses in connection with them, and to 
earth. At this second station (b) we have therefore a second 
break in the electrical circuit, and it is easily seen that, in 
order to pass the current through and fire any particular 
fuse, both these breaks must be bridged over, under which 
circumstances the circuit of the battery will be completed 
and the mine fired. Let us now suppose a vessel to be ap- 
proaching this line of mines, as her bow passed across the 
production of the line (b m 5 ,) the observer at (b) would put 
down the key Xo. 5, in connection with (m 5 ;) but as the ship 
had not come into the line from («,) passing through the line 
of mines, the observer at (a) would not put down his key, a 
break would still exist in the circuit, and no current could 
pass to fire the mine. When the vessel had passed the line 
(b m 5 ,) the observer at (b) would allow the key to spring up 
and break the connection. As the vessel passed the line 
(b m 4 ,) the observer at (b) would press down key Xo. 4, but 
as she would still not come on the intersection of the lines 
(b m 4 ) and (a m 4 ,) the same result as before would be obtained, 
and the charge (m 4 ) would not be fired. Let us now suppose 
that she passes on in her course till she arrived over the 
mine (m 3 ;) in this position she would be on the intersection 
of the two visual lines (am 2 ) and (b m 3 ;) the observers at (a) 
and (b) would in this case both put down their respective 
keys simultaneously, the circuit of the battery would be 
completed through the mine (m 3? ) and that mine would be 
fired. In the case of a vessel passing through an interval 
between any two mines, at such a distance as to be out of 
the radius of destructive effect of either of them, as, forexam- 
ple, at the point (s x ) between (Wi) and (m 2 ,) it is easily seen that 
at the moment of passing the line (a m 1? ) when the observer at 
(a) would have his key down, she would not be on the pro- 
duction of any of the liues (b mj, b m 2 , &c.,) and as the observer 
at (b) would not under such circumstances press down his 
key, she would pass on to the second line (n h n 2l &c 7 ) and 



188 

having passed safely through the interval of the first line 
would stand a good chance of coming within striking dis- 
tance of one of the mines of the second. For this second 
line (wi, w 2 , &c.) a similar but separate arrangement should 
be prepared. 
Firing by a pre- A simplification of this plan may occasionally be adopted 
at one station? 113 by employing a preconcerted signal at the point (a) when 
the bow of a vessel came on the line (a m^) For instance, 
if, when the bow of the vessel (s) arrived on the line (a m 3j ) 
a flag were raised at the point (a,) the observer at(ft) would 
instantly notice whether she was on any of the lines of 
sight passing over his mines, and if she were, would at 
once press down the key corresponding therewith, as Eo. 3, 
shown in the Fig. 79. Directly she had passed the line (a m u ) 
the flag at (a) should be dropped, as she would then be safe 



Fig t 79. 




c % 

so far. as that line was concerned. This latter system 
requires great coolness and nerve on the part of the obser- 
ver at (&,) as he has two things to do, viz, to watch the ves- 
sel passing across his intersections, and to be on the alert 
to receive the signal from (a.) In such a case it has been 



189 



found best to employ two men at station (/;,) one exclusively 
to watch the station (a,) and on the flag being- raised to 
give the word " fire,' 7 and on the flag being dropped to give 
the word u stop," the second man would keep his eye on the 
vessel, and be ready to fire the right mine at the right 
moment. A separate signal-flag and firing arrangement 
would, as before, be required for the next line (^ n& &c.) 
of mines. 



/j\ % 80. 



/ i \ 




#!#No 



separate intersec- 

so far advanced toward the tions for each 



As in many cases it would not be practicable to have a 
station in such a position as (a 

point of attack, with the corresponding danger of being cut 
off by an enemy, another combination becomes necessary; 
this is shown in Fig. 80. Two stations (a) and (&,) well within 
the defensive works, are selected in such a position that the 



190 

lines, passing from them over each charge, shall intersect in 
such a manner as to give what is termed a well-conditioned 
triangle, or, in other words, that they shall not intersect each 
other at too oblique an angle. The battery is placed at 
the point («,) one pole being attached to earth, while tile 
other is connected with a center from which radiate a series 
of contact-keys. From the studs or contact-points of these 
keys a series of cables, corresponding in number to the 
charges in i>osition, pass to the similar contact-points of a 
similar set of keys at the station (&,) and from the pivots of 
the keys at (b) an electrical cable passes to each charge. 
In this case, therefore, each charge has a separate key at 
station (a) and a separate key at station (&,) each perfectly 
distinct from every other, and well insulated therefrom, but 
the whole culminating at (a) in the single battery (c z.) In 
each circuit, corresponding to any particular mine, there 
are therefore two breaks, one at its particular contact-key 
at the station (a,) and the other at its corresponding key at 
station (&,) and till these breaks are bridged over, by 
pressing down the contact-keys simultaneously, the cir- 
cuit of the battery will not be closed and the mine will 
not be fired. In this way it is easily seen that if, for 
example, key No. 1 is put down at the station (a,) and 
key No. 2 at station (&,) there still remains a break in 
each circuit ; in circuit No. 1 at station (b) and in circuit 
No. 2 at station («,)*and neither of these mines will be fired. 
The object of this arrangement is easily seen if we trace 
the course of the vessel (s) approaching the line of mines. 
She first comes on the line of (m 5 ) from station (a,) and 
simultaneously on that of (mi) from station (&;) the observer 
at {a) puts down key No. 5, and the observer at (6) key No. 
1, without of course firing any mine ; again, as she reaches 
the position ($ 1? ) the observer at (a) would put down key 
No. 4, and the observer at (b) key No. 2, without any circuit 
being closed. Let us now suppose her to reach the point 
(8 2 ) when the lines from both stations over the charge (w 3 ) 
intersect; both observers would now put down keys No. 3 
simultaneously, the circuit of mine (m 3 ) would be closed, 
the charge would be fired, and the vessel struck. 
Pickets may be In carrying on the system above described, it has been 
tion d a f r 8 hort r dis- found that with a series of small wooden pickets, placed in 
tances. a ra diating form from a central point of observation, at a 

distance of about twenty feet, and with pieces of twine 
passing from the center over the pickets in the direction of 
the charges, to indicate the bearing more accurately, very 
good practice has been obtained, all the charges having, at a 
distance of a quarter of a mile, been exploded within a radius 



191 



of six feet of the object aimed at. The observer, with his 
eye at the central picket and his right hand on the contact- 
keys, puts the corresponding one down as the object passes 
the bearing of each. A man soon learns by practice the 
distauce he may allow on one side or other of the bearing- 
line, and with ordinary care and nerve is soon able to make 
contact at the right moment. There is no doubt, however, 
that on actual service the steadiest and coolest meu would 
be required to work such a system effectually. 

The following is a description of the firing-keys recom- 
mended, and shown in plan and section in Fig. 81. The 



Firing-keys 



e e © e © e 




apparatus consists of an oblong wooden box, 8 inches long by 6 
inches broad, and 2| inches deep, within which are firmly 
fixed two ebonite bars, (a) and (&,) one close to each of the 
larger sides ; the object of these is to insulate the several 
wires, connected to binding-screws (c c c, &c.,) on the bar 
(a,) and (d d d, &c.,) on the bar (&,) from each other. One 



192 

set of insulated wires (/ / /, &c.) may be carried into the 
box and attached to the binding screws (c c c, &c.,) another 
set [g g g, &c.,) maybe connected with the binding screws 
(d d d, &c.) The firing-key (i) consists of a strong metal, 
spring, in metallic contact with the binding screw (d) and 
thence to the cable (g) attached to it, and with an insulated 
knob, (7*,) by which its metallic point may be pressed down 
upon the binding screw, (c,) which latter is in metallic con- 
• tact with the cable (/) attached to it. It is thus easily seen 
how by pressing down any one of these keys a metallic cir- 
cuit is established from the cable (/,) on one side, to the cor- 
responding cable (#,) on the other side of the box, and that 
before the key is pressed down there is no metallic circuit, 
and consequently no path for the electric current. 

The box is provided with a wooden lid to keep the keys 
safe when not in use, and there is an India rubber diaphragm 
let into this lid, just over the keys, through which they may 
be depressed when the lid is shut. Two screw-holes are also 
provided by which the whole box may be firmly fastened to 
a table or bench when required. 
connections of In the combination shown in Fig. 78, a single key only 

keys for use. -,-,, . , . \ -i-ii • -i 

would be required at the station (a;) this would be similar 
in construction to any single key of the set shown in Pig. 
81, one pole of the battery (c z) being put to earth; the 
other would be connected to the binding screw (c,) while 
the cable connecting stations (a) and (&,) Fig. 78, would be con- 
nected with the binding screw (d,) Fig. 81, and the power 
of changing the cable from the firing-battery would be ob- 
tained by simply putting down and holding down the firing- 
key. At station (&,) Fig. 78, one firing-key would be re- 
quired for each mine. All the wires (///, &c.,) Fig. 81, 
having been denuded of insulation close to the box, would 
be brought together and soldered carefully to the single 
conductor, carried from station (a) to station (b 7 ) Fig. 78, 
while from the binding screws (d d d, &c.,) Fig. 81, a separate 
insulated cable would be laid to each mine. For the arrange- 
ment shown in Fig. 79 only one set of keys would be re- 
quired, the battery being connected to the whole of the rear 
binding screws, with the separate cables radiating from the 
point. If used in the combination shown in Fig. 80, two 
complete sets of keys would be required, arranged as de- 
scribed for Fig. 78, with this difference, that a separate con- 
nection for each minewonld.be necessary from the front 
binding screws of the firing-keys at station (a) to the rear 
binding screws of the set of keys at station (&,) the bat- 
tery being in connection with each and every one of the 
rear binding screws of the set of keys at station (a.) 



193 

In using the keys it is necessary to press them firmly 
down and hold thein firmly down, iu order to insure good 
contact at the proper moment. 

To work efficiently it does not seem desirable that more 
than six keys should be intrusted to the management of 
any one man. 

The system of pickets, above described, for giving the Telescopic ar- 
bearings, might probably be used effectually up 1 to half a 
mile, but at greater distances a more accurate means of 
obtaining the intersections becomes necessary; the pickets 
have, moreover, the disadvantage of being easily disturbed 
and difficult to replace in an accurate position if once moved, 
In order, as far as possible, to obviate these defects, a tele- 
scope with cross wires has been mounted in connection with 
a series of contact-points and a movable key, as shown in 
Fig. 82. 

It consists of a solid and somewhat heavy cast-iron stand, Details of teie- 

i-i-i ^ • • 1 +- /7\ l-i- SC °P ic firing in " 

(«.,) on which is placed an iron upright (b) arranged to carry strument. 
a telescope with cross wires, (c,) the latter having a horizon- 
tal and vertical motion. The object of giving considerable 
weight to the cast-iron stand is to obviate, as far as possible, 
the chance of the displacement of the whole instrument by 
the concussion of guns fired in its vicinity. Two circular 
holes are cut in the body of the stand to reduce its weight, 
which would otherwise be unnecessarily great. A circular 
level (cl) attached to the cast-iron stand gives the means of 
leveling it with sufficient accuracy, by means of three cap- 
stan-headed screws, (e e e.) Though this instrument, in con- 
sequence of its weight, is not 'very susceptible of displace- 
ment by concussion, it would always be advisable to place 
it as far as possible from the neighborhood of heavy guns 
in action, the concussion produced by their discharge being 
very great. Between the iron upright (&,) and insulated 
from it and the telescope by a ring of ebonite, is a brass 
portion, (/,) into which fits a brass arm, (</,) at one 
end of which is a wooden handle, (h,) and at the other 
a binding-screw. This arm and the portion (/) of the 
upright in connection with it forms, as will be hereafter 
explained, a portion of the electric circuit when the instru- 
ment is connected up for certain operations ; it is therefore 
made of brass to prevent the chance of oxide in the con- 
nections, which might increase the electrical resistance. 
The arm {(j) is rigidly connected, through the upright (tf,) 
with the telescope and moves with it. It traverses over an arc 
(k) described with a radius of not less than eighteen inches, 
and supported at its two extremities by thick iron uprights 
13 



194 

(I I.) This arc consists of an iron frame, in two pieces, di- 
vided longitudinally in the center, the upper portions being 
faced with ebonite, in order to insulate the two parts from 
each other and from the metallic contact points (m m, &c.) 
in connection with them, for reasons to be hereafter explained. 
The arc is marked with divisions by means of which the 
position of the contact points {mm, &c.) maybe registered, 

Fig. 82. 





so that, in the event of their being accidentally displaced, 
they may again be fixed in true relative position with facility. 



195 

These divisions serve also to determine the position of the 
whole instrument in the following manner : The telescope is 
directed on some distinctly marked object, snch as a flagstaff 
or the defined angle of a building, and the number of the 
division under the guiding spring of the handle (h) of the 
brass rod, with the telescope in that position noted, it is 
thus easily seen how, even if the whole apparatus is moved, 
it may be replaced in the same position with facility, pro- 
vided the position of the point immediately beneath the 
upright (6) supporting the telescope and on which the in- 
strument revolves, or of the three capstan -headed screws, 
has been carefully marked. Fixed to the lower part of the 
brass arm (g) is a metal spring, in connection with a metal 
contact point; motion is given to this latter by an ebonite 
knob (n) attached to it by a small upright bar, passing through 
the arm (g.) In a state of rest the spring holds this contact 
arrangement up close to the arm (#,) but the depression of 
the knob (n) moves it downward sufficiently to bring it in 
connection with any of the contacts (m m, &c.) which may 
be directly beneath it. The knob (n) is made of insulating 
material, because the arm (g) is always charged with elec- 
tricity at the moment of action, and the operator would 
receive a shock were the knob allowed to remain uninsulated. 
For the same reason it is necessary to insulate the eye-piece of 
the telescope, because it, too, is in metallic connection with 
the arm (#,) and would consequently be similarly charged. 
The extremity (h) of the arm (g) is made of an insulating 
material (wood) for the same reason. 

Fig. 83 shows an enlarged section of the extremity of the ta( 
arm with the contacts and other arrangements in its vicinity; 
(g) is the brass arm, and (h) the wooden extremity or handle ; 
in connection with the latter is an ebonite block (a) just long 
enough to rest upon the outer iron arc (c,) and thus to pre- 
vent the contact point (d) being brought down except by 
the depression of the knob (n ;) (b) is a small steel spring 
attached to the ebonite block (a) which, by touching a pro- 
jection of the lower contact arrangement, gives an indicatiou 
that the latter is vertically under the upper contact-point 
(d;) (e) is a brass ring which fits tightly over the arm (#,) 
and the spring (/') connecting it with the upper contact 
point (d.) When this is drawn back to the position shown in 
Fig. 83, no accidental depression of the knob (n) could occur, 
and no accidental ignition of a charge could take place. 
For work, the ring (e) is pushed forward and the spring (/) 
released. The lower contact arrangement consists of two 
metallic portions (ii,) separated and insulated from each other 
by an ebonite dividing-piece (k.) These metallic portions 



Detail of con' 



196 



are provided with shoulders made to fit upon them the upper 
ebonite portions of the arc (I I,) and with a thin projecting 
arm, giving the means of making contact with the spring 
(&,) as already described. The lower contact arrangement 
is'fixed firmly in position by means of an ebonite wedge (m,) 
passing through it and pressing against the metal portions 
of the arc (c c.) In metallic connection with the brass por- 
tions (i i) of the lower contact arrangement are two thick 
copper wires (o) and (p) to which the battery or line circuits, 
&c, may be attached. When the upper contact point (d) 



Fig. 83. 




To place 
instrument 
position. 



is depressed, as in the position shown by the dotted lines, 
it will be observed that the insulated space (1c) between the 
two sides (i i) is bridged over. 
the To place the instrument in position, a point from whence 
iU the lines of mines are clearly distinguishable should be 
chosen. This point should be as far as possible from heavy 
gums and the foundation should be moderately solid. A 
broad flat stone, for example, would furnish a convenient 
foundation on which to place the apparatus. The iron 
stand of the instrument having been leveled, by means ol 



197 

the circular level and capstan-headed screws, the telescope 
should he directed on some fixed and well-defined object, 
and the number of the division under the spring of the handle 
registered. The telescope should then be directed on each 
mine or line of mines, as the case may be, in succession, the 
position of the mines having been marked by buoys or 
other similar means for purposes of identification, and one 
of the contact arrangements brought into proper position 
for each, and keyed firmly up, and the number of the mine 
and the number of the division on the graduated arc regis- 
tered. This having been done at one or both stations, as 
required, the buoys marking the position of the mines may 
be removed. The points where the capstan-headed screws, 
carrying the instrument, rest, should be carefully marked, 
so that the whole may be replaced in the same position if 
accidentally disturbed. Should it stand on a stone, small 
shallow holes might be cut to receive the points of these 
screws with advantage. 

The mode of using this instrument is similar to that for thJtastrument ing 
the firing-keys, Fig. 81, already described. It is, however, 
adapted for longer distances. 

For such a combination as that shown in Fig. 78, two in- 
struments would be required ; for that used at station fa,) 
the battery would be connected with each of the rear wires 
fo, o, &c.J Fig. 83, of the lower contact arrangement ; the 
electric cable from (a) to fb,) Fig. 78, would be attached to 
the binding-screw in connection with the upright ff.) Fig. 

82, carrying the telescope. At station fb,) Fig. 78, the electric 
cable arriving from station fa) would be attached to the 
binding-screw ff,) Fig. 82, while the cables connecting its 
several mines would be attached to the rear wires fo,) Fig. 

83, of the lower contact arrangement. It is thus easily seen 
how the depression of the key of the instrument at station 
(a J Fig. 78, would change the cable from fa) to fb,) and, 
through it, the brass arm of the instrument at station 
fb,) and that the depression of the key at station fb) would 
pass the charge on and complete the circuit through any 
one of the mines fm m, &c.) required. Unless both keys 
were down simultaneously no current could pass, and, as 
already explained with reference to the firing-keys, Fig. 
81, both keys would not be down together unless an 
enemy's vessel were at the point of intersection of the two 
lines passing over a mine, and the telescopes were both 
directed on her. 

For the combination shown in Fig. 79, the firing-battery 
would be connected with the binding-screw (/,) Fig. 82, and 



198 

the cables connecting the mines with the rear wires (o o, 
&c.,) Fig. 83, of the lower contact arrangement. 

For the combination shown in Fig. 80, the battery at sta- 
tion (a) would be connected with the binding screw (/,) Fig. 
82, the cables connecting stations (a and b) with the rear 
wire (o o, &c.,) of the lower contact arrangements; while at 
station (&,) Fig. 80, the electric cables arriving from station 
(a) would be connected to the front wires (p p, &c.,) Fig. 83, 
of the lower contact arrangements, and the conductors thence 
to the charges would be connected with the rear wires (o o, 
&c.) In this case the necessity for dividing the metallic 
portion of the lower contact arrangement, b} r means of the 
insulating ebonite center, becomes evident. 

The description given is that of an instrument now in 
use at the School of Military Engineering, Chatham, for 
instructional purposes. This is probably one of the first 
that has ever been made, and though it works with consid- 
erable accuracy, improvements will, no doubt, in time be 
introduced. For example, with a radius of eighteen inches, 
an interval of 50 yards between two mines in a line subtends 
a very small arc at a distance of a mile, and the contact 
arrangements are brought very close to each other. This 
defect may be remedied by making the contact points 
smaller, or by using a second instrument for every alternate 
mine. 
Arrangement of For a line of mines a fixed telescope, with a single firing 
andfiringkeysforkey, might be employed with advantage. With such an 
a lme of mmes. aiTan g emen t it would be only necessary for the observer to 
keep his eye on a vessel, and, the moment she arrived at 
the cross wires of his telescope, to press down his key and 
keep it down until she had fairly passed. 
simplicity is es- It has even been suggested that each mine, in the combi- 
iaSgeme 1 nt s a for nation shown in Fig. 80, should be provided with two fixed 
bearings. 7 cr ° 8S telescopes, one at each of the stations (a) and (&.) In this 
way an observer would have but one object to engage his 
attention and but one duty to perform, viz, to put his key 
down when a vessel arrived on the line of his own particular 
mine. There is no doubt that simplicity of arrangement is 
most essential in firing by visual intersections, and it is 
very probable that if several vessels were simultaneously 
approaching a line of mines, which were connected with a 
telescopic or other arrangement, in which one man had 
charge of several firing keys, he might be engaged in observ- 
ing one vessel, while his fellow-workman was directing his 
instrument on another, and many ships might thus pass 
through uninjured. It unquestionably requires much more 



199 



dexterity, nerve, and training to work a number of keys, 
combined with a movable telescope in one instrument, than 
to watch a vessel approaching a mine, on which a single 
fixed telescope was directed, and to put down a single key 
on her passing the cross- wires. 

We now come to the different modes of firing electrical Mechanical 

cuit-closers. 

submarine mines mechanically, that is to say, by an arrange- 
ment through which the vessel herself closes the circuit, by 
means of an apparatus called a circuit-closer. 

A great number of different forms of this instrument have 
been made, each possessing certain advantages. 

In the Austrian section of the Paris exhibition a circuit- Austrian circuit 
closer was exhibited in connection with the torpedoes. 

In this system the submarine mine and circuit-closer are 
in the same case. The details of the circuit closer are shown 
in Fig. 84 ; (b b b) are the buffers, held in position by strong 

fto.84, 



closers. 





brass springs, the openings through which they pass being 
kept water-tight by means of strong mackintosh cloth ; when 
pressed in they would come in contact with, and cause to 
revolve, a brass rachet- wheel (#,) also kept in position by a 
strong spring. 

Strong pieces of wood (h h h) round the circuit-closer 
keep the buffers and their attached arms in the proper 
direction, and give rigidity to the part of the iron cylinder 
through which they pass. 

The brass ratchet-wheel (g) being put in motion, carries 
round with it a central arrangement (i,) the lower part (that 
nearest the fuse) of which is shown in detail in Fig. 84. 
This central portion consists of a brass cylinder (&,) divided 
into two portions, insulated from each other by a division of 
ebonite (?,) shown in black; one side of this cylinder is fit- 
ted with three arms of brass (m, w, and o,) and the other 
with two arms (p, and #,) all of which are carefully insu- 
lated from each other by India rubber. The arm (m) is close 
to, but insulated from, a metal plate (r,) which latter is per- 
manently connected with the conducting wire from the bat- 



200 

tery, and thus in its state of rest remains electrically 
charged. Beyond the arm (n) is a small spring (s,) perma- 
nently connected with the earth, and in such a position that 
when the central portion is moved round, this spring (s) 
comes in contact with the arm (n) and the plate (r) with 
the arm (m) simultaneously, and the circuit is completed 
through earth to the battery, without, however, passing 
through the fuse. 

Referring again to Fig. 84, the arms (o and p) on oppo- 
site sides of the brass cylinder and consequently insulated 
from each other, are connected with the fuse, and the arm 
(q) is permanently connected with the earth. 

"We left the current passing from the battery through the 
arm (m) by the brass cylinder to the arm (n) and by the 
spring (s,) then in contact therewith, to earth, and complet- 
ing the circuit; but by a still further pressure of the vessel 
on the buffer, the arm (h) is pushed beyond the spring, 
and in contact therewith, and consequently circuit by earth 
to the battery is broken, while the contact of the arm (m) 
and plate (r) is still retained, and the current is passed by 
the arm (o) through the fuse to the arm (2?,) and then to 
earth through the arm (#,) completing the circuit through 
and firing the fuse. 

The action of the spring, in breaking the circuit, has the 
effect of intensifying the current (by means of an intensity- 
coil in connection with the firing battery) to its utmost 
extent, and at the moment when this intensity is highest, 
passing it through the fuse. 
to render a Should a friendly vessel be approaching a line of mines 

channel safe for a _. ,, . , .. -ii-it , 

friendly vessel, arranged on this system, it would only be necessary to 
detach the firing battery, by removing the connecting plug, 
to render her passage perfectly safe. Should she make con- 
tact with any of the mines in her course, the ratchet-wheel 
(#,) Fig. 84, would be pushed round, the spring (s) would 
make and break contact, as before described, but no 
current would be circulated; and on the vessel leaving the 
mine the ratchet-wheel would be drawn back to its original 
position, by means of a strong spring in connection with it, 
and be ready again to act when required. The arrange- 
ment for closing the circuit is made sufficiently strong to 
prevent chance of injury from contact with a friendly vessel. 
Fuse only in It will be observed that, in the Austrian system, the fuse 
rnenT* of th fir?n°g is only put into the electrical circuit at the moment when 
mine " it becomes necessary to fire it. This arrangement was con- 

sidered necessary, to obviate the chance of the accidental 
ignition of a change from induction, caused by atmospheric 



201 

electricity. According to Baron Yon Ebner, accidents of 
this nature have occurred to mines used by him. This mode 
of cutting the fuse out of circuit till the moment of ignition, 
guards most effectually against such an occurrence, but, at the 
same time, it renders it impossible to fire the charge at will> 
and the ignition of the mine is thus reduced to that single 
condition in which the action of the circuit-closer, by the 
contact of a vessel, is essential. 

Another form, designed by F. Abel, esq., F. E. S., chem- 
ist of the war department, is shown in section and elevation 
in Fig. So. It consists of a strong wooden case («,) bound 
with four iron bands (&, &, b, &,) buoyancy being given to it 
by means of an air-tight chamber (c.) Within the apparatus 
is a brass tube (rf,) into the lower extremity of which a pair 
of insulated wires (e) and (/) are introduced, by means of 
a joint (g) inclosed in a stuffing-box. This latter is rendered 
water-tight by a ring of India rubber, shown in black in 
section, compressed against the insulation of the conducting 
wires by the action of a screw working on the extremity of 
the brass tube (d.) In order to render this joint thoroughly 
water-tight, the insulation of the two wires (e) and (/) is, 
at this point, welded into one, and made into an elongated 
oval form, thicker than the original insulation, by the addi- 
tion of layers of Chatterton's compound and gutta-percha 
in a plastic state. In thus welding the insulation care must 
be taken to prevent the two conducting wires from being 
accidentally pressed into contact while the gutta-percha is 
softened by the heat necessarily applied. Within the brass 
tube (d) is another tube of brass or iron (7t,) extending ver- 
tically through the whole apparatus, and working on an 
universal joint (i) at its lower extremity. The upper portion 
of this tube is rigidly connected with a metal bar (&,) which 
latter is firmly attached to a strong teak top (I,) supported 
on the wooden case (a,) and separated from it by a vulcan- 
ized India-rubber ring (m.) It is thus easily seen how any 
blow on the top would be transmitted to the metal cylinder 
(/«.) The interior of the brass cylinder (d) is kept water- 
tight by means of a vulcanized India-rubber collar (;i,) shown 
in black in section, connecting it with a ring projecting from 
the metal bar (k.) A couple of metal screws (o o) are made 
to fit on a screw tapped on to the upper portion of the metal 
bar (A-,) and, by means of a spanner, these may be screwed 
down so as to firmly connect the top of the arrangement 
with the wooden top (I.) One of the insulated conducting 
wires (e,) having been carried in through the metal tube 
(7i,) is soldered on to a copper ring (p) incircling the bar (A-,) 



Abel' 
closer. 



202 

but insulated therefrom. The insulated conductiiig-wire 
(/) is passed through a hole in the tube (h,) and its bared 
extremity is attached to a binding-screw (q) in connection 



7" 



fe0 



Fig. 85. 



r^\ 




o^ 



LJ 




with an insulated brass band, let into a broad ebonite ring 
which passes completely round a hollow, in the brass tube, 
made to receive it. To the base of the apparatus feet (r, r, r) 






203 

are attached, on which it may stand in such a way as to 
keep the projecting piece (g) clear of the ground. Rings 
are formed in these feet for the attachment of the mooring- 
chains. A ring (s) is attached to the upper portion of the 
apparatus to facilitate manipulation and moving the circuit- 
closer. A metal ring (t) is let into the opening of the upper 
portion of the case (a) to take the weight of the outer case 
when the circuit-closer is lifted by the ring (s.) A thick 
ring (t') of vulcanized India rubber keeps the whole combi- 
nation rigid, and by its resistance, dependent on its thick- 
ness, regulates the force which must be used to set the 
apparatus in action. 
This circuit-closer is designed for use, so that the fuse may Mode of using 

= ' the apparatus. 

either be kept entirely out of the circuit till the moment 
when it is required to be fired, as in the Austrian system, 
or it may be employed in the ordinary manner with the fuse 
in circuit as usual. In the latter case only one wire is re- 
quired, and this is connected with the copper ring (p 5) the 
insulated brass band is not then required, and the space 
allotted to it is filled by metal. 

For the former combination the electric cable from the connection with 
firing battery is connected with the insulated wire (e,) the circuit tin the mo- 
other pole of the battery being to earth, the wire (/) being men ° lgailon - 
attached, through an insulated conductor, to one pole of the 
fuse, and a metallic connection being arranged from the 
other pole of the fuse to earth. In order to fire the fuse it 
is easily seen that it is only necessary to bridge over the 
space between the copper ring (p,) to which the wire (e) is 
connected, and the brass ring (q) attached to the wire (/.) 
This would be done by a vessel striking the top (e) of the 
apparatus in any direction, which, being pressed on one side, 
would carry with it the bar (&,) and, by the action of the 
universal joint (i 7 ) bring some part of the copper ring (p) in 
contact with the brass band (#,) thus completing the elec- 
trical circuit. In this combination it is easily seen how the 
fuse is onl}- introduced into the circuit at the moment when 
it is required to be fired. 

When it is desired to arrange the fuse in connection with connection 
this circuit-closer in the ordinary manner, the combination ^cuitM 2uai. m 
is as follows : One pole of the firing-battery being to earth, 
the other is connected, through the electric cable, with one 
pole of rhe fuse, the other pole of the fuse being placed in 
metallic connection with the insulated wire (e,) while the 
insulated wire (/) is put to earth by being connected with 
the metallic portion of the case (a.) In this combination 
it is easily seen that, in order to fire the fuse, it is only neces- 



204 

sary to bridge over the space between the two brass rings 

(p) and (#,) which would be done, as already described, by 

the action of a vessel striking the top of the apparatus. 

Advantages and When the fuse is entirely out of the circuit till the moment 

nation, with° ftJe of ignition, it cannot be fired at will, and cannot be tested 

out of c?rcuft. in ° r except when a return wire is used ; it is, however, manifestly 

very safe from accidental ignition. On the other hand, 

when the fuse is arranged between the firing battery and 

the circuit-closer, any considerable fault in the insulation, 

between the fuse and the circuit-closer, would be very likely 

to cause an accidental explosion. 

to render a j n order to render a channel safe for a friendly vessel, it 

channel safe for a ^ ' 

friendly vessel, would only be necessary, in either of these combinations, 
to detach the firing battery, in which case, should a circuit- 
closer be struck, it would re-establish itself in its former 
condition by virtue of the action of the flat India-rubber ring 
(V) and the collar (?£,) and be ready to act effectively as 
before. 

A^ ci<?n % i of From experiments carried on at Chatham with several 

er - circuit-closers of the form described, it has been proved that 

they are very efficient in action, and that the strong external 
wooden case possesses sufficient resisting power to enable 
them to stand a good deal of knocking about and rough 
usage, without damage to the internal circuit-closing arrange- 
ments. This power to resist heavy blows is essential to the 
efficiency of any form of circuit-closer, as, when in position 
in a channel through which there is much traffic, they are 
always liable to be struck with considerable force by blades 
of screws, floats of paddles, and other hard and sharp bodies. 
It would be an improvement if the stuffing-box (g) were 
arranged to be flush with, or at least to extend as little as 
possible below, the bottom of the apparatus. Its projection, 
as shown in Fig. 85, renders it very liable to injury from a 
side blow. This improvement might no doubt be very easily 
effected, but the same object has been attained, in the most 
recent pattern of this circuit-closer, by fixing a stout metal 
cap over this stuffing-box, the conducting cable being brought 
out through a lateral opening. 
Mathieson's in- Another form, designed by Quartermaster- Sergeant J. 

tltiacircuitcloser -Mathieson, E. E., is shown in Fig. S6. 

It consists of a wrought-iron dome (a,) with a flange at 
its foot, to enable it to be attached to an iron bottom piece 
(&,) by means of screws and nuts, in such a manner that it 
may be removed at will, the whole top coming bodily off, so 
as to give easy access to the inside where the circuit-closing 
apparatus is arranged. The joint between the flange and 



205 

bottom piece is made water- tight by means of an India-rub- 
ber ring, compressed between the two portions at the joint j 
(c) is a strong wooden cover, made of deal, saturated with 
tar, fitting. closely over the dome, and bound by strong iron 




bands (d, d, d,) which latter, being attached by screws and 
nuts to the foot plate (&,) connect the whole apparatus firmly 
together, and enable it to be moved with safety by the ring 
(e,) which is strongly fixed on to the iron bands (d d) at the 
top of the apparatus for this purpose. The cover (c) is 
made of light wood, in order to assist in giving buoyancy 
to the whole, in addition to which it must be strong enough 
to protect it from heavy blows, such as those which would 
be given by the blade of a screw or any similar hard and 
sharp substance. The circuit-closing arrangement consists 



206 

of a brass ring (/,/) with four metal springs (#, g) attached 
to and projecting below it, at equal distances from each 
other, (every quarter of a circle.) This metal ring is sup- 
ported by four uprights (h, h 3 ) made of brass, so that the 
ring itself is kept in metallic connection with the iron bottom 
piece (&,) and at the same time firmly attached thereto. 
Within the apparatus is a strong flexible iron rod (£,) to 
the top of which is attached a ball of lead (n,) while at its 
center is a brass disk (m,) the outer rim of which, as well 
as the inner surfaces of the four projecting springs (#, g,) 
is platinized, to prevent oxidation, which would impede 
metallic contact ; the center of the disk (m) is of ebonite, to 
insulate it from the rod (I.) The insulated wire (■£,) for con- 
nection with the electric cable from the fuse and firing bat- 
tery, passes in through the bottom piece (h) at the point (ft,) 
by means of a joint on Mathieson's principle, somewhat 
similar to that described at page 134. From the joint (k\ 
the insulated wire is carried to a binding-screw on the disk 
(m,) the whole being thus kept insulated till the moment it 
becomes necessary to close the circuit. A ring (o) ispro- 
vided at the bottom for the attachment of the moorings, 
and the whole is supported on three feet (p, p, p,) for facil- 
ity of working on shore. These feet prevent any chance of 
injury to the electric connection (i) by the apparatus resting 
upon it. Holes are provided in these feet to which the 
moorings may be attached. All the iron work connected 
with the apparatus is galvanized. 
connections for, The general principles on which the instrument is con- 
se - nected for use may be described as follows : One pole of 

the firing battery being to earth, the other is connected 
with the insulated electric cables, and through it with 
one pole of the fuse*, the other pole of the fuse being- 
attached to an insulated wire, to connect it with the con- 
ductor {i) permanently fixed in the instrument. This last 
connection is made by means ofMathieson's joint, as described 
at page 134. 
Mode of action. The apparatus is put in action by a blow in the external 
wooden case (c,) which causes the flexible rod (I) to move 
on one side from the inertia of the weight (n) at its upper 
extremity. This brings the platinized brass disk (m) in contact 
with one of the projecting springs (g g.) The whole of the 
iron work of the bottom plate and instrument generally 
forms, when immersed in water, an excellent earth-plate- 
and the ring (f) being in metalic connection with it, it is 
easily seen how, by the motion of the disk (.»,) the insulat- 
ing space between it and one of the four stprings attached 



207 

to that ring (/,) is bridged over and the circuit closed for 
an instant. A vessel striking a circuit-closer of this nature 
would thus mechanically fire a charge in connection with 
it, and to render it safe for a friendly ship it would only be 
necessary to detach the firing battery. 
In order to regulate the sensitiveness of the instrument, Regulation of 

, , , , sensitiveness of in- 

two screws, with washers, oue above and the other below Btmment. 
the ball (»,) give the power of regulating its position on the 
rod (I.) To make the apparatus more sensitive the leverage 
is increased by fixing the ball high up on the rod ; to make 
it less sensitive it is placed low down. The means of regu- 
lating it in this manner is given by a screw tapped on to 
the upper extremity of the rod (I.) The duration of the 
contacts made by this apparatus have been measured by 
means of a Morse recording instrument placed in a circuit 
with it. When struck by a passing vessel a succession of 
contacts occur, the first much shorter than the others. The 
following is a fac simile of a strip of paper, on which the 
contacts were thus recorded, which will give a very good 
idea of the action of the instrument: 




wire 
fuse. 



This circuit-closer may be used either with Abel's or the May be used 

*" with Abel's or 

platinum wire fuse, and is especially efficient with the latter, platinum 
in consequence of the comparatively long duration of its 
contacts. This effect of a somewhat prolonged contact is 
no doubt due to the flexibility of the rod (Z,) which, after the 
first blow, carries the weight (n) rather beyond that point 
where a simple light contact would result, and the small 
interval of time is that necessary for the apparatus to 
recover itself. 

This circuit-closer has been very severely tried at Chatham, ^^S.^ 
and has proved itself very efficient. Several specimens have 
been moored in the ship channel of the river Medway, oppo- 
site Gillingham, during the years 1869 and 1870. In this 
position they have been subjected to rough weather and 
hard knocks from passing vessels, and experiments have 
been made in moving them and hauling them up for exami- 
nation. Some of them have been kept submerged for sev- 
eral months, during which time they have proved efficient 
when tested, and, when taken up, been found to have re- 
sisted successfully the very severe Usage to which they had 



208 

been subjected, and to be as fit for work as when first put 
in the water. There appears to be no action of the ball, 
caused by the regular swing of such a sea as occurs in this 
part of the Meclway, and indeed it would seem to be quite 
safe for use in any sea, however heavy, for it has been 
swayed about, when afloat, by means of a boat-hook, so as 
to briug it down nearly to a horizontal position. When this 
motion is given smoothly and regularly no contact, as indi- 
cated by a galvanometer or other instrument in circuit, has 
ever occurred when the ball has been properly adjusted. 
The slightest concussion, however, will set the apparatus in 
action ; circuit-closers, which had successfully resisted the 
operation of swinging down on their sides by means of a 
boat-hook, having been in every case set in action by the 

External coyer- impact of a small boat rowed against them. The external 
protection Against wooden covering has also proved a most efficient protection 
against rough usage. The wood and iron work of many of 
these circuit closers have been found deeply indented by 
blows from the screws and paddles of steamers wiien they 
have been taken up after long submergence, while the 
interior has remained quite uninjured and in as good work- 
ing order as when first put in the water. The proportion 
of the diameter of the pear-shaped upper portion may be 
increased considerably over that shown in Fig. 80. A 
greater diameter at this point w r ould increase the chance of 
contact with a passing vessel, as well as tend to make the 
apparatus float more vertically in the water. 

This apparatus, which has been entirely designed by 
Quartermaster-Sergeant J. Mathieson, E. E., is a very effi- 
cient piece of mechanism. While possessing sufficient 
solidity of construction to resist external injury, it has 
proved itself so sensitive that a very slight blow will put it 
in action, and though it is possible that improvements may 
hereafter be made in it, or that other forms of circuit-closers 
may be designed, there is no doubt that it might be at once 
used with success in connection with any system of subma- 
rine mines. 

Mathieson'M cir- Another similar apparatus, differing however in its mode 
of action, has been designed by Quartermaster-Sergeant 
J. Mathieson, E. E. Iu it the current is allowed to circulate 
continuously, and the effect of a blow is, for an instant, to 
interrupt the electrical current with a corresponding cessa- 
tion of the current ; it is easily understood how this cessation 
of current would convey a signal to the testing-room, and 
how it might, by means of a relay, be made available for 



cuit-breakei 



209 

throwing a firing-battery into the main circuit. From its 
mode of operation it has been called a "circuit-breaker." 

Its general arrangements are shown in Fig. 87 ; (a) is a Construction of 
brass casting, forming the base of the instrument, with a 
projecting rim to supply the place of the feet in the original 
design ; (6) is a brass dome similar to that already described ; 
(c) is a disk firmly attached to a steel rod (d ;) the center of 
this disk is composed of ebonite to insulate it from the rod, 
while its outer portion is of brass as before ; (e) and (I) are 
the earth and line wires arranged for introduction into the 
apparatus by means of an ebonite screw-piece (&;) (h) is a 
cylindrical ebonite block, shown also in plan, to which are 
attached four strong brass springs (/, /, /,/) projecting 
downward somewhat below the level of the disk (c,).and 
in such a position that any deflection of the rod carrying 
the latter would bring it in contact with the springs and 
press them outward. The lower portion of this block (7i) 
is of smaller diameter than the upper, and through it pass 
four brass screws (g, g, g, g) corresponding to the brass 
springs, and with their points outward and in contact with 
them ; (i i) are brass pillars supporting the ebonite block (h-,) 
(j) is a ball of lead firmly attached to the steel rod (d.) The 
electrical connection between the screws (g, //, g, g) and the 
springs (/, /, /, /) is made in the following manner : the line 
wire (?) is attached by means of a binding-screw to the first 
screw, which presses against the first spring ; from the top 
of this first spring an insulated wire is carried to the second 
screw, which presses against the second spring; the top of 
this second spring is similarly connected by an insulated wire 
with the third screw pressing against the third spring, the 
top of which is again connected with the fourth screw press- 
ing against the fourth or last spring, the top of which being 
connected, by means of a binding-screw, with the earth 
wire (e,) completes the combination. These connections are 
shown by the dotted lines in the plan of the lower portion 
of the ebonite block; there is no connection between the 
top of the fourth or last spring and the first screw ; any 
current, therefore, arriving along the line-wire passes to the 
first screw, thence to the top of the first spring, thence to 
the second screw and second spring, and so on to the last 
spring and to earth, and a deflection of any one of the 
springs, causing an interval between it and its correspond- 
ing screw, would, as may be easily understood, break the 
electrical circuit and cause a cessation of the flow of the 
current. The whole is inclosed in a solid wooden covering, 
as described for the original apparatus. 
14 



210 

Several improvements have been made in the construc- 
tion of this instrument. It will be observed that the dome 
(b) is connected with the foot-plate (a) by means of a screw, 
on the diameter of the former, which brings pressure to bear 
upon a gutta-percha ring permanently and firmly imbedded 
in a circular recess formed in the latter, making the whole 
water-tight. The wooden covering is strongly attached by 
means of bolts, passing through the projecting foot of the 
base piece and secured by nuts. 

Quartermaster-Sergeant Mathieson proposes to cover the 
point of entry of the earth and line wires with wood, to pro- 
tect the conducting wires ; it is doubtful whether a metal 
dome would not be more efficient for this purpose. 
connections for To connect the instrument for work, the signaling bat- 
^ti?n and mode ° f t ei T is attached, through the relay or other signaling 
apparatus and electric cable, with the line wire (?,) and the 
current passes thence by the insulated wire to the first brass 
screw, and as long as the points of the screws (#, g, g, g) 
corresponding to the springs (/, /, /, /) remain in contact 
with them, it passes freely through the combination and to 
earth by the earth wire (e,) completing the circuit through 
the earth connection of the other pole of the signaling bat- 
tery. Should the apparatus receive a blow from a vessel, 
the action of the weight (j) would deflect the rod (d) and 
bring the disk (c) in contact with one of the springs (/?/,/,/,) 
pressing the latter away from the point of the screw (g) in 
contact with it, and, for an instant, creating a break in the 
electrical circuit and making a signal on the instrument in 
the testing-room of the fort connected with it. The mass 
of the cylindrical block (h) being of ebonite, it is easily 
understood how the electrical circuit is only completed by 
the coutact of the springs (/, /, /, f) and the points of the 
screws (g, g, g, #,) and that pressure, forcing any one of these 
springs on one side, must cause a break in that circuit till, 
by its elasticity, the instrument had recovered its normal 
position. 
Regulation o f The mode of regulating the sensitiveness of this instru- 
Sriiment B of ment is an improvement on that originally designed. The 
ball (j) is permanently fixed on the steel rod (d,) and the 
screws (#, #, #, g) are capable of being moved in or out, so 
as to exercise more or less pressure on the springs in con- 
tact with them ; the amount of pressure thus regulates the 
degree of sensitiveness with very great nicety, 
contacts of ^ n or( ^ er to insure good metallic contact between the 
pS z a ed 4springs P° ints of the screws (fc 9, ff, 9) a»d the springs (/,/,/,/,) 
and to prevent chance of oxide or other interruptions to the 



211 

passage of the current, the points of the screws and the 
faces of the springs in contact with them are platinized. 

The instrument may be converted into a circnit-closer by Arrangement for 

* t .,. ,, ... , ., converting instru- 

simply detaching the line wire (?) from the screw (</,) and mentinto a circuit- 
connecting it, by means of the binding-screw (m) with the cc 
metal disk in connection with the flexible steel rod (d.) With 
this arrangement a' blow from a ship would close the circuit 
by establishing a metallic contact between the metal edge 
of the disk (c) and one of the springs (/,/,/,/,) from whence 
the current would pass through the combination of screws 
and springs attached to the ebonite block (h,) and thence 
to earth by the earth wire (e.) To fit the apparatus for use 
as a circnit-closer, the edge of the metal disk (c) must be 
platinized, for the same reason as given in the case of the 
screw points. 
Qnartermaster-Sergeant Mathieson's original idea, on pendulum cir- 

cu.it -closer 

which the instruments above described are improvements, 
was that of a weight arranged in the form of a pendulum. 
It was, however, too sensitive for actual practice; though 
excellent in still water, it was easily affected by a compara- 
tively slight swell, and was consequently abandoned. 

Lieutenant E. F. Moore, E. E., has suggested a circuit- Pendulum cir 
closer on the pendulum principle. It is simply a common gested by Lieuten- 
bell, the clapper of which is insulated from the body, and re. ' 
the circuit is closed by bringing the former in metallic con- 
tact with the latter. This apparatus has not been suffi- 
ciently tried; being similar in principle to Mathieson's pen- 
dulum, it is to be feared that it would fail from similar causes. 

It would no doubt stand the regular and uniform swing 
produced by a sea, as Mathieson's did, for a considerable 
time, but the slightest deranging influence caused the latter 
to close the circuit, and it is difficult to understand how it 
could act in one case and not in the other. 

Another form of circuit-closer, suggested by Quarter- Mathieson's dual- 
master-Sergeant Mathieson, E. E., may be described as fol- cioting ' x arrange- 
low s: It consists of a glass vessel containing, and at the ment " 
same time insulating, the earth connection. This glass ves- 
sel is so arranged that a ship would come in contact with 
and break it. when the circuit would be completed by the 
earth plate through the water, and the charge fired. 

He proposes to moor his mines in pairs, at a depth of 
about 3' below the surface of the water, and to sustain them 
in that position by means of small surface floats, possessing 
just sufficient buoyancy to keep them in position without 
being too conspicuous, as described in page 82. Though 
this arrangement has not been found to answer, in consc- 



Mode of action, 



212 

quence of the reasons given in the description referred to, 
there is no reason why the mines themselves might not he 
floated up from sinkers on the bottom in the usual way, 
though they would not, under such circumstances, be effect- 
ive at all times of tide. He proposes to connect each of the' 
mines to a hermetically- sealed vessel, placed midway be- 
tween them, by means of strong lines. He proposes to carry 
his electric cable from the firing battery on shore to a point 
on the bottom nearly midway between the pair of mines, 
containing the electrical connection by branches thence to 
the fuse in each mine, and from each fuse to an earth-plate 
inclosed within the glass vessel between them. 

A ship passing between a pair of such mines would throw 
a strain on the lines connecting them with the glass vessel, 
the mines themselves would be drawn toward the ship's 
sides, the glass vessel would be broken, the earth-plate con- 
tained in it would be brought in contact with the water, and 
the pole of the firing battery not connected with the electric 
cable being to earth, the charge would be fired. 

In the event of a vessel being observed to pass without 
exploding the mines, Quartermaster -Sergeant Mathieson 
proposes an alternate mode of firing by the frictional elec- 
trical machine ; by means of a switch-pin the battery would 
be disconnected and the frictional machine, with its con- 
denser ready charged and earth connection made good, 
thrown into circuit. On the condenser being discharged, 
the small length of cable beyond the fuse would act, in con- 
junction with the surrounding water, as a Leyden jar, and 
the tension of the charge produced by this very powerful 
machine, combined with the inductive action set up between 
the metallic conductor forming the inner, and the water, 
forming the outer coating of the Leyden jar, would be suf- 
ficient to fire a high-tension fuse. The platinum-wire fuse 
could not be used in this combination. 
Experiments to Experiments were tried at Chatham on the 18th of May, 

test power of fir- _,__ , „ . 

iug by frictional 1870, to test the power of the frictional machine to fire a 
smaii_ length of charge by induction in this way. A cable, half a mile long, 
L e a Leyden jar? consisting of a strand of 7 No. 22 B. W. G. copper wires, in- 
sulated to j 3 ^ inch with Hooper's patent di-electric, was 
laid out on the ground and a fuse attached to the fuse end 
with 12 feet of electric cable beyond it, the latter immersed 
in water, but with its end carefully insulated. Under these 
conditions AbePs fuses were fired with certainty by a port- 
able ebonite Austrian frictional machine, not only when 
applied directly to the cable to which the fuse was attached, 
but by induction when a charge was passed through half 



213 

a mile of similar cable, laid parallel to it on the ground at 
a distance of three feet. A battery of 100 Darnell's cells 
failed to fire the fuse by induction under either of the cir- 
cumstance's specified. 

In such a combination care must be taken to leave plenty 
of slack in the electric cable, so that the strain may not 
come on them, but on the lines connecting the glass vessel 
with tbe mines. 

This system possesses the disadvantage that, unless it Disadvantages of 
was so arranged that the mines could be drawn down out esystt 
of the way, the first vessel, friendly or otherwise, which 
passed through would break the glass vessel and probably 
also the electric cables connecting it with the mines. By 
simply detaching the firing-battery no injury need occur to 
a friendly vessel ; but even -if the electrical connections 
remained in working order, the mines would be reduced to 
the condition of being capable of being fired at will only. 
Charges might be arranged to be hauled down, under certain 
circumstances, to allow friendly vessels to pass, but as a rule 
this would be a very difficult operation and probably not appli- 
cable to the majority of cases. The power of the frictional ma- 
chine to fire charges arranged in this way is, no doubt, very 
great, but the danger of induction when using it must not 
be lost sight of, — see description in pages 170, 171, and 
172, — and its employment must therefore be limited to con- 
ditions in which this serious disadvantage may not be pro- 
ductive of unintended results. 

These are some of the most practical forms of circuit- 
closers capable of application under various conditions, but 
no doubt others might be designed suitable for the purpose. ■ 

Most circuit-closers are capable of being used either in circuit-closer 
the same case as the charge, or detached from it and only with mlnes^r de- 
connected by a suitable mooring line and electric cable. In tached from them ' 
the Austrian system the circuit-closer and charge are in 
part of the same case, and are so arranged that the charge 
will only explode when a vessel is in actual contact with it, 
or nearly so. The reason of this is that the Austrian mili- 
tary authorities were of opinion that, to be effective, a 
charge must be fired in very close proximity to a vessel's 
hull. 

One advantage arising from a combination, in a single 
case, of the circuit- closer and charge, is the additional 
inertia thus obtained proportioned to the weight of the 
latter. The general tendency of any body floating in water, 
on being struck by a ship, is to move easily on one side, 
and thus to lessen the force of the blow; the greater inertia 



214 

of the combined charge and circuit-closer is therefore in 
favor of the effective action of the circuit-closing appa- 
ratus. 
cifn-ciosS ci ro" The floating obstruction committee have proposed a de- 
posed by floating tached circuit-closer, trusting to the extension of the de- 

obstruction com- 70 

mittee. structive effect due to the explosion of any given charge 

extending to a certain distance from it. What this distance 
is has yet to be definitely determined, but experiments prove 
that it is not limited to actual contact with the charge, 
though it diminishes rapidly in proportion to the increased 
cushion of water intervening, as the distance from the side 
of a vessel increases. There is no doubt that in a tidal 
harbor or estuary, a detached circuit-closer presents many 
advantages, one of which is that the position of the actual 
charge may be arranged so as to suit the ever varying 
depths of water over it with greater facility, when the cir- 
cuit-closer is detached from it. It is probable that neither 
detached circuit-closers nor those permanently combined with 
the charge can be universally adopted ; measures have 
therefore been taken to design different cases for each com- 
bination. Mathieson's circuit- closer is readily adaptable to 
either. 
Enemy would The first object of an enemy in attacking a harbor de- 
dei? minis ineSc- fended by submarine mines would be, if possible, to explode 
tive - those mines, and thus render the ground in his front safe ; 

or, failing to do this, to get hold of and carry off the cir- 
cuit-closers, and, if possible, to dispose of the electrical 
cables in connection with them in such a way as to render 
the charges unexplodable ; and as is it not desirable to throw 
away large charges upon boats and small craft, such as 
would be employed in the duty of searching for mines, means 
must be taken to retain the charges intact and effective, 
even should the circuit-closer be carried away. 
power of firing Should an enemy simply break away a circuit-closer, and 

ine should be re- 
tained, if possible, 
after remova 
circuit-closer. 

were arranged in circuit as in Fig. 88. Supposing the cir- 
cuit-closer (n) removed, the fractured conducting cable would 
still, in most cases, be sufficient to pass the current to earth 
in the circuit of the battery (c z) being completed, and this 
operation could easily be performed within the testing-room. 
Under these circumstances the mine would remain as effect- 
ive as ever, provided the means of ascertaining the posi- 
tion of a vessel existed. Supposing, however, that an 
enemy, knowing the arrangements prepared for his recep- 
tion, were, before casting off the broken end of the conductor, 



mine should be re- allow the end af the e i ectr i c cable to fall off, there would, 
of of course, be no difficulty in still firing at will, if the fuse 



215 



a 






after detaching the circuit closer carefully to iusulate the 
fracture, the charge (m) would, under such circuiustauces, 
be almost harmless. It might possibly be fired by in- 
duction with the friction - 
al machine, as already 
described, if there were 
a sufficient length of 
conductor beyond the 
QXJ fuse and a high-tension 
fuse were used, but this 
would be a difficult and 
uncertain result to ob- 
tain. 

In order to obviate 
such a contingency a 
different combination 
has been proposed by 
Quartermaster- Sergeant 
Mathieson, E. E., which 
is well deserving of at- 
tention, from the great in- 
genuity displayed in all 
its arrangements. Fig. 
89 shows the general de- 
sign of the system. The 
electric cable passes di- 
rect from the battery 
(c z) to one pole of the 
fuse in the charge (m,) 
the other pole being di- 
rectly connected to 
earth, and there is a 
branch to the circuit- 
closer (n 7 ) starting from 
a point (a) between the battery and the fuse. In this 
case the circuit-closer is simply used as an indicator, and 
may be made to work a relay in a manner to be hereafter 
described. When in a state of rest the extremity of the 
cable, passing from (a) to (n,) is manifestly insulated, and it 
is evideut that the charge (m) may be exploded at any mo- 
ment at will, by simply completing the circuit of the battery 
(c z) in the testing-room. Let us now suppose that an 
enemy, knowing the system of firing adopted by the defenders, 
has got possession of the circuit-closer (n,) he would, under 
such circumstances, detach, and having removed the insu- 
lation from a considerable portion of the extremity of the 



N- 



216 



conducting wire, be would throw it into the sea, so that the 
current, finding an easier path through the bare end of the 
wirejthan through the fuse, would pass almost entirely in 



.Low water line.-. Fk. 89. 



>7V 



EHlllillll 



772/ 




Mathieson's dis-that direction and not fire the fuse 

ment would, however, prevent such a contingency 

Fig, go. 



The following arrange- 
Fig. 90 





shows in section a combination by which the two extremities 
(a a 1 ) of a break in the electric cable, leading from the fork 
or branch in the vicinity of the charge, are introduced into 
an ebonite vessel (&,) so that, when held in an upright posi- 
tion, a small quantity of mercury (c) placed therein would 
complete the circuit. If the vessel (b) were inverted the 
mercury would fall down to its larger extremity, and the 
circuit would be broken. Should the vessel only fall over 
on one side the same effect would be secured, for directly 
the contact between the mercury and the two extremities 
of the wire (a a') ceased, the electrical circuit would be 
broken, and the extremity (a) of the cable, to all intents 
and purposes, effectually insulated. If an enemy, therefore, 
were to get possession of a ciruit-closer attached to a cable 



217 

arranged in this way, and cut and cast it off, under the sup- 
position that lie was connecting the circuit to earth and 
thns rendering himself secure, the falling away of the mer- 
cury would insure the insulation of the point («,) and the 
mine (m,) Fig. 89, would still remain as efficient as ever. 

A modification of the device above described, suggested Disconnector de- 
bv Lieutenant Anderson, R.E., consists in the substitution of ant Anderson, r. 

• " F 

a platinized metal ball in a platinized metalcup for the mer- 
cury. One of the wires is attached to each side of the 
metal cup, and the two sides of the cup, and conse- 
quently the points of the wires are insulated from each 
other. As long as the ebonite vessel remains upright, the 
ball completes the circuit between the two extremities of 
the wire, but directly it is turned over the ball falls out, 
and the two sides of the cup, one attached to each wire, 
being insulated from each other, the circuit would be imme- 
diately broken. 

Suppose now that an enemy, knowing that an arrange- Electromagnetic 

disconnector. 

ment ot the nature above described was used, were to get 
possession of a circuit-closer, he would carefully detach it, 
make the end of the wire bare, so as to complete the circuit 
to earth, and bury it, so as to keep the ebonite ■ cup up- 
right, and retain the mercury or platinized ball in such a 
position as to complete the circuit. To guard against such 
a contingency another arrangement has been suggested by 
Quartermaster-Sergeant J. Mathieson. He proposes to intro- 
duce an electro-magnet between the point (a,) Fig. 89, and 
the circuit-closer, the armature of which should be in con 
nection with a spring, arranged as in the primary circuit of 
Bhumkotf's induction coil, so that it would make and 
break the circuit mechanically with great rapidity. With 
such a combination as this it is easily seen that every alter- 
nate instantaneous current would pass through the fuse in 
the mine (m) and fire it. With such arrangement it would 
not matter whether an enemy were to insulate the wire, 
after detaching the circuit-closer, or not, as the power of 
firing the charge at will would remain in the hands of the 
defenders under both conditions. It would not, however, 
be available for use with the frictional machine. 

These disconnecting arrangements, in the form described, Further trials 
have none of them been sufficiently tried to enable a defiuite reqmred - 
opinion to be given as to their practical use. They are, 
nevertheless, interesting, as illustrations of the general 
form of combinations which might be used to counteract an 
enemy's attempts to render a system of submarine mines 
ineffective. Should any modification of the branch system, 



218 

shown in Fig. 89, be adopted, it is manifest that some dis- 
connecting* arrangement mnst be employed, in order to meet 
the contingency of a removal of a circuit-closer, and there 
seems to be no reason why one or other of the very ingeni- 
ous expedients proposed may not be made capable of prac- 
tical application. 

There is no doubt that it would be a very great waste of 
power to fire large mines, of 500 pounds of gun-cotton, for 
example, at boats engaged in searching for them, and such 
boats might, relying on the immunity thus secured, carry 
on their operations with comparative boldness. In day- 
light it is probable that they might be kept off by the gnns 
covering a system of mines, or by boats manned by the 
defenders; but at night, or in a fog, they might carry on 
their operations in comparative security as regards such 
means of defense; the question is, therefore, whether some 
plan might not be adopted to act as a deterrent without, at 
Arrangement of the same time, sacrificing the principal mine. It has been 

cS?u\t-Sas r e g r! s m suggested, for example, that a small charge, sufficient to sink 
a boat without damaging the large charge, might be placed 
in the circuit-closer and arranged to be fired when that cir- 
cuit-closer was touched. In order to secure this effect some 
such combination as the following might be adopted : A 
single fuse might be placed in the charge in the circuit- 
closer, the latter being connected, as shown in Fig. 89, with 
a branch circuit from the point (a,) while in the main charge 
a number of fuses might be placed in continuous circuit, or 
with a considerable electrical resistance, in the shape of a 
coil, or an ordinary lightning protector might be arranged 
between the point (a) and the fuses in the charge (m.) Now, 
if a battery sufficient to fire a single fuse were arranged in 
connection with a circuit so constituted, directly the circuit 
through the circuit closer was completed, by touching the 
latter the charge therein would be fired, and any small 
boat in its vicinity sunk or damaged, while from the great 
resistance introduced between the point (a) and the fuses in 
the main charge these latter would remain intact, but could 
still be fired by a considerable increase in the power of 
the firing-battery, or by the friction al or dynamo-electric 
machine, provided the end or the branch connecting the 
point (a) with the circuit-closer were insulated when blown 
off, and this could be effected by means of the mercury-cup 
or other arrangements already described. 
Difficulties at- Such a combination, however, must be attended with 

charg' g of U cir e cuu- difficulties. In the first place, it becomes necessary so to 
balance the respective resistances of the fuse in the circuit- 



219 

closer and those in the main charge, as to render the sim- 
ultaneous explosion of the two charges impossible. To do 
this a largely preponderating resistance mnst be given to 
the circuit in the main charge, and in order subsequently 
to fire the latter with certainty a large increase of battery- 
power would be necessary. This adjustment of resistances 
in the fuses, as well as subsequently in the battery-power, 
would at all times be a delicate operation and require the 
greatest care. Again, the circuit- closer must be at such a 
distance from the mine itself that the explosion of the 
charge contained in it shall not damage the case or connec- 
tions of the latter. A charge of 5 pounds of gun-cotton would 
probably be sufficient to sink any boat, but it would be 
necessary to ascertain how far such a charge must be 
•placed from others in its neighborhood to insure their safety. 
Again, it is not desirable to expend the circuit-closer 
attached to a mine, except as a last resource, because as 
soon as it is gone the mine can only be fired by judgment. 
It is a choice of evils, however, and preferable to allowing 
an enemy to carry off the circuit-closer without damage to 
himself. 

In order to determine whether such a system can be prac- 
tically worked, carefully conducted experiments are neces- 
sary. 

Another mode of keeping off boats would be to place a Advanced line 

,. . of contact mine 

hue of small contact charges m advance of the mam line, for defense against 
a line of supports as it were. There can be no doubt that 
the sinking of a few boats would produce a very salutary 
effect as regards the defense. 

If fhese charges were sufficiently large to damage, if not 
to sink, vessels of any size, a further advantage would accrue, 
Contact charges of 100 pounds of gun-cotton would not be 
very bulky to handle, and would no doubt be effective in 
an advanced system of this sort, even against vessels of the 
largest size ; and if exploded by the smaller craft their loss 
would not materially affect the main defense, 



CHAPTER XII. 



ELECTRICAL TESTING-TABLES. 



We now come to the consideration of testing-tables, or, 
in other words, the mode of arranging the wires in connection 
with the charges in a convenient form in the electrical-room 
within a fort. When a very large number of wires must be 
introduced into a fort, it becomes necessary to arrange»them 
in such a manner that they shall be easily identified, and 
that the operations of testing and firing, &c., may be con- 
ducted with the greatest amount of simplicity. Several 
forms of tables have been designed with this object in view. 
The Austrian government exhibited several instruments of 
this nature at Paris in 1867. One of these, which gives a 
good general idea of their system, may be described as 
follows : 
^Austrian testing- Its design is shown in Fig 91; {c, z) represents the bat- 

Fig. 91. 



& 






9 9 929 

.[111! 



999 

8 



If 



9 9 9 9 9 9 9 

& jo ii 12 ij Mil 



9 




wb 



^S 



tery with one pole to earth at (<?,) and the other in connec- 
tion with an intensity coil (a,) through which the current 
passes to the contact plate (6.) When it is desired to put 
the system of mines, in connection with the table, in a state 
of preparation to be fired by the contact of a vessel, a plug- 
is inserted between the contact plates (b and /,) and the 



an exploded 
ge. 



221 

current passes through unci electrically charges the. conduct- 
ing wires, shown by dotted lines, connecting the charges 
with the battery, through the several binding screws (g, g 1 
g, &c. ;) as soon, therefore, as a vessel makes contact, the 
circuit is completed, as already described, (see page 186,) and 
the charge fired. 

It then becomes necessary to ascertain which particular Test to discover 
mine of the system has been exploded ; for this purpose thenar 
plug is placed so as to connect the contact plates (b and d,) 
the current is then passed on to the testing circuit, shown 
by the firm lines, in which a galvanometer, (/i,) is placed, and 
which is in connection with two metal bars (i 7c\ i 7c;) 
on these bars, and slipping freely along them, are metal 
keys (1 and m ? ) sufficiently long to complete the circuit from 
them to the binding- screws (</, g, g, &c.) 

In a state of rest these keys are thrown back into the posi- 
tion in which (?) is shown, and no current passes beyond 
the bars (i 7c, i 7c;) when, however, the key is turned over 
into the position in which (m) is shown, the current passes 
into and electrically charges the insulated wire communi- 
cating with the mine; in this way each of the binding-screws 
({/, g, g, &c.) is put in circuit in succession, and on arrival 
at that lately in connection with the charge that has been 
fired, the galvanometer will be deflected, as the circuit will 
be completed by the broken end of the conducting wire, 
through the water, and back by the earth-plate to the battery. 

In order to test the insulation of the electric cables con- 
necting the mines with the battery, (the firing circuit,) it is 
only necessary to place the plug between the contact-plates 
(b and d) and touch each of the binding-screws (g, g,g, &c.,) 
in succession with the testing key ; should the galvanometer 
(1i) remain stationery, the insulation is good; but should 
a leak exist, the current passing through it would act on 
and deflect the galvanometer, indicating the particular line 
in which it exists, and, roughly, the extent of the leak in 
proportion to the deflection shown; should the leak be con- 
siderable, the defective cable should be at once detached, as 
the current lost through it might so diminish the working 
X)Ower of the battery as to prevent its firing an} T of the fuses 
attached to the group in connection with the same battery. 
For the same reason the conducting wire of an exploded 
charge should be at once disconnected from its binding- 
screw. By the above arrangement the insulation of each 
line can be tested at any moment required. 

In order to make the channel safe for a friendly vessel, it 
is only necessary to remove the plug' from between the con- channel 



Insulation test,. 



222 

tact plates (b and/) and insert it between (b and d,) or leave 
it out altogether ; this disconnects the battery from the 
firing circuit. 

Great care should be taken to keep the metal keys (I and 
m) always throw T n back, except at the moment when re- 
quired for use in testing, in order to avoid the chance of 
accidents. 
ba S tter arate enerin g " ^ would be convenient in most cases to employ a sepa- 
used - rate battery for testing ; this might easily be done by ar- 

ranging a special battery in connection with the galvanom- 
eter and testing circuits. Should hostile vessels be in the 
act of passing over the system of mines, it would not do to 
detach the firing battery for testing purposes, and yet it 
might become necessary to ascertain which electric cable 
should be detached in the event of a charge being fired ; in 
such a case a special testing-battery would be indispensable, 
and in some of the instruments exhibited such a battery 
was provided. To test the insulation of the electric cables, 
however, which would, except on an emergency, always be 
done when an enemy's vessel was not in the vicinity of the 
mines, the greater electro- motive force of the firing-battery 
would be advantageous, a smaller leak in an electric cable 
w T ould be more readily discovered 5 and as that cable would, 
in actual work, always be charged with the full power of 
the firing-battery, the value of its insulation to resist an 
electrical charge at such a high potential would be an im- 
portant point to determine. The fuses being entirely oat 
of circuit until the moment of action arrives, no danger of 
a premature explosion need be apprehended ; if a fuse were 
in such a position as to be fired prematurely, it would be 
exploded, in connection with the firing-circuit, independently 
of the operation of testing the insulation of the cables. 

The form of testing-table described is that used in con- 
nection with the Austrian self-acting system of contact 
mines. Other combinations adapted to various conditions, 
such as firing by judgment, &c, were also exhibited. 
Testing-tabie ^ simple arrangement of testing- table is shown in Fig. 
where fidng-bat- 92, in this combination a series of metallic points (d d d, 

iery is put m cir- x \ T 

cuit by hand. &c.,) are in metallic connection, through a series of galva- 
nometers (g g #, &c.,) with the line wires, fuses (m m m, &c.,) 
and earth-plates {e x ei e h &c.) The galvanometers (g g g, 
&c.) are not very sensitive, just sufficiently so to indicate 
directly the passage of such a current as would be produced 
by closing the circuit of a battery of two or three of Dau- 
ielPs cells, as (c 2 £2,) by the action of a circuit-closer, one of* 
a set placed on a series of branches, as (n n n, &c.,) so as for 



223 



the moment to cut out the fuses (m m m, &c.) in tlie man- 
ner already described. Another series of contact points 
(///, &e.) are in connection with one pole of a firing-bat- 

fig. 92. 



VZ *4 C£ Q 

<0 <J <D ™ft) 



h-0 

n 




tery (ci z h ) the other pole being to earth. In order to fire 
any of the mines at will, it is evident that it only remains 
to close the circuit of the battery (ci Zi) by completing the 
connection between the points (d d d, &c.) and (///, &c. ;) 
this is effected by the simple depression of a key which is 
arranged to be done by hand. Another set of contact 
points (a a a. &c.) are in connection, through a very delicate Testing and 
galvanometer (g,) with a testing battery (c 3 s 3 .) Fig. 93 signaliug circuit *- 
shows an enlarged plan and elevation of a firing-key. Con- 
tact plugs are provided, which, in their ordinary position, 



-key. 



224 

would remain between the contact plates (b and c ;) and the 
front arm of the firing-key being in connection, when in a 
state of rest, with the point (6) and pivoted on the contact 



jfip. 03. 




point (tf,) the current of the signaling battery (c 2 z 2 ) would 
be free to pass through the contact points (c b) and (<?,) and 
along the line wire ; and the completion of any individual 
circuit, through its own circuit-closer, would be indicated 
on it's corresponding galvanometer of the series (g g g, &c.) 
In order to test any individual line and fuse it would ouly 
be necessary to remove the contact plug from between the 
plates (b and c) and insert it between (a and &,) by which 
operation the signaling-battery (c 2 sfc) would be thrown out, 
and the testing-battery (c 3 z 3 ) and galvanometer (g) would 
be thrown into the circuit, and the deflection of the latter 
would indicate whether ail was right as regards insulation 
and conductivity. During this process of testing, it will 
be observed that the line and charge tested would only be 
thrown out of the ordinary conditions ; the remainder of the 
charges would remain in statu quo and be ready to indicate 
that a vessel was within the radius of destruction at any 
moment. The ordinary galvanometers (g g </, &c.) would 
at all times give a rough indication of the effectiveness or 
otherwise of the line and fuse. 

The key employed for firing is precisely of the form used 
with the ordinary Morse telegraph instrument. In a state 
of rest the front contact is held down on the plate (h) by 
means of a spiral spring ($,) and to fire it is only necessary 
to depress the handle (h) and make contact with the plate 
(/,) aud, the key being pivoted on the point (d,) the effect 
of this depression would be simultaneously to break contact 
with the point (&.) Thus, the firing-battery would be thrown 
into circuit and the signaling-battery cut out simultaneously 
by the depression of the key. 
To detach eh-- When any given charge has been fired, it would only be 
nit ut expended iiecessary to remove the plug from between the plates (b 



225 

and c) in order to cutoff the conducting cables which would 
otherwise interfere detrimentally with the action of the in- 
tact circuits, and which, after a charge has been fired, should 
be detached with as little delay as possible. If the circuit 
were cut off in this way the line wire itself would be dis- 
connected from the system at leisure, an operation which 
it might not be convenient to perform immediately, in the 
heat of action with an enemy's vessels in the act of passing- 
over the mines. In this system it will be observed that the 
tiring battery is only thrown into the circuit at the wish of 
the operator, and that no mine can be exploded without the 
depression of its corresponding key. In order, however, to 
render the system perfectly safe, and to guard against the 
accidental depression of the key, which would produce a 
premature explosion, a plug has been provided between the 
tiring-battery and the apparatus, at the poiut [p;) when 
this plug is out the firing- battery cannot be accidentally 
thrown into circuit. 

The construction of a testing and firing table of this consmmion of 
nature is so simple that it could be very easily put together ve? y sLpS 
by an ordinary workman, and the materials of which it is 
composed are obtainable anywhere. The mines in connec- 
tion with it are capable of being fired by judgment, and, for 
this purpose, would only require the addition of signaling 
apparatus, somewhat similar to that described on page 186 
and those following, to complete the system, which could 
thus be used for firing by intersection when the position of 
the mines was clearly visible, while capable of being used 
at night or in a fog, on the signal being made by a vessel 
in contact, as first described. It is, however, dependent 
for effective service upon the vigilance and dexterity of the 
man in charge, which is a defect common to all systems in 
which firing by judgment is employed. 

This arrangement of testing-table may be used either May be 
on the circuit-closing or circuit-breaking system. With the 
circuit-closing system it would be connected precisely as 
shown in Fig. 89 ; with the circuit-breaking system, the 
circuit-breaker would be placed beyond the fuse, and this 
signaling current, passing through it, would keep the gal- 
vanometers deflected on a vessel striking any one of them, 
the action on the galvanometer would cease, and its needle 
would fall back to the position due to terrestrial magnetic 
attraction, and this motion of the needle would indicate the 
fact of the ship's contact. 

The system above described is so arranged as to indicate 
a vessel in contact with a circuit-closer, and as in many 
15 



either with a cir- 
cuit-closing or cir- 
cuit-breaking sys- 



226 



cases it may be convenient or even necessary to perforin 
the operation of throwing in the firing-battery without the 
aid of a personal operator, the following self-acting system 
has been devised : By making the apparatus purely self- 
acting, all chance of error, consequent upon the inattention 
or want of dexterity of the man in charge, is, of course, 
eliminated, and this may be done without complicating the 
connections of the instrument to any considerable degree. 

&X- 94- 




shutter-signai- Fig. 94 shows a diagram of the arrangements by whichaves- 
■paratus. llDg ' ap ' sel striking a circuit-closer may be made to shift, by means of 
a relay, the conducting cable from the signaling to the 
firing-circuit and explode the charge; called the " shutter- 
signaling and firing-apparatus." 

(a) is an armature, working on a pivot between the two 
horns of an electro -magnet (b &,) and held in position by a 
spiral spring (c;) the latter is in connection with a regula- 
ting screw, by which more or less pressure may be brought 
to bear in an opposite direction to that of the attractive 
action of the electro-magnet. A small stud (i) regulates the 
distance to which the armature may be drawn back ; (d) is 
a shutter, on which a reference number is clearly indicated, at- 



227 

tacked to a lever pivoted at the point (0,) the inner arm of which 
is just long enough to catch under the point of the armature 
(a;) when a current is passed through the coils (b b) of the 
electro-magnet, the armature (a) being attracted, the lever 
attached to the shutter is released, and the latter falls by its 
own weight into the position shown by the dotted lines. The 
pivot (e) is formed of an ebonite cylinder, with a metal, cen- 
ter, from which latter two metal points project through the 
ebonite. When the lever (/) is held up by the armature (a,) one 
of these metal points projects downward and is in contact with 
a metal spring (#,) which forms a portion of the circuit of the 
signaling-battery. When the shutter falls into the posi- 
tion indicated by the dotted lines, the other metal point, 
projecting through the ebonite cylinder, comes in contact 
with a metal spring (/&,) which forms a portion of the circuit 
of the firing-battery, while the connection between the spring 
(g) and its corresponding point is broken in consequence 
of the revolution of the pivot bringing the ebonite part of 
the cylinder upon it. The metallic portion of the axis (e,) 
being permanently connected with the line wire terminal, 
and through it with the electric cable and fuse in the charge, 
it is easily understood how the action of dropping the shut- 
ter throws the firing-battery into circuit, and simultane- 
ously cuts out the signaling-battery and explodes the mine. 
The points of the metal projections on the pivot (e) and the 
faces of the springs (g and h) are platinized, to prevent 
oxide and insure good metallic contact between the parts. 
The armature (a) is prevented from coming into actual con- 
tact with the horns of the electro-magnet, by two small 
studs. The object of this is to prevent any effect of residual 
magnetism which might interfere with the rapidity of action 
of the armature when released and drawn back by the 
spring (c.) 

Ttie signaling-battery should be so constituted as to be constitution of 

signaling-battery. 

capable of working the electro-magnet effectually when the 
circuit is closed direct to earth, and attracting the arma- 
ture with sufficient force to release the lever (/) with cer- 
tainty, and yet not so powerful as, by the continuous pas- 
sage of the current generated by it, to fire the fuse in the 
mine. Plenty of power may be given to this battery, when 
used in connection with a platinum fuse, without any chance 
of accidental explosion from this cause, but when Abel's 
fuse is employed it is necessary to be very careful in order 
to guard against such a contingency. 

The testing arrangements are precisely the same as those ^1^* 8 "" 
shown in Fig. 93 $ it is, however, necessary to disconnect 



228 

the firing battery in this latter combination, when testing, 
as any accidental dropping of the shutter would produce a 
premature explosion. 

Firing-battery. The firing-battery should be suited to the nature of the 
fuse employed, and should possess considerable excess of 
power in order to overcome accidental defects, such as in- 
creased resistance in the connections or defective insulation 
in the electric cable in connection with the mine. A battery, 
just sufficiently powerful to fire a fuse on shore, with the 
electric cable, &c, in circuit, but not submerged, would not 
be unlikely to fail after the cable had been immersed in sea- 
water; in such a case it is recommended that the battery 
power determined by such an experiment on shore should 
be doubled for actual work. 

Mode of action If used in connection with a group of mines, arranged 
of the apparatus. with c i rcu it-closers on the branch system, as shown in Fig. 
89, the mode of action of the apparatus would be as follows : 
while at rest the current of the signaling-battery would 
be divided between the several fuses in circuit; each of 
these fuses, possessing a very high electrical resistance, 
would, by its presence in the circuit, prevent the battery 
current, passing the coils of the instrument, acting with 
sufficient force to form an electro- magnet, sufficiently power- 
ful to overcome the resistance of the spring (c) and draw 
the armature (a) over to it. Directly, however, one of the 
circuit-closers on a branch was struck, the whole of the 
fuses would be, for an instant, practically cut out of circuit, 
because the resistance of those fuses, compared with that 
of the earth connection of the circuit-closer, is so great that 
practically the whole current would pass through the one 
particular circuit-closer that had been struck. When this 
took place the comparatively feeble current of the signaling- 
battery would therefore practically be passed through a 
single electro-magnet, (that in connection with the circuit- 
closer struck,) and would consequently act with sufficient 
force to attract the armature, which it had not power to do 
when divided between the several fuses (each possessing a 
very high electrical resistance) in the group. The arma- 
ture (a) being attracted, the lever (/) would be released, 
the shutter would fall, and the firing-battery would be 
thrown into circuit, through the spring (h,) and the metal 
point in contact with the pivot (e;) the coils of the electro- 
magnet being simultaneously cut out of circuit, as already 
described, the current of the firing-battery, having a direct 
metallic circuit through the fuse to earth, would pass instan- 
taneously through and fire the mine. The action of the 



229 

whole is so rapid that practically the instant a vessel struck 
the circuit-closer the mine would be fired. 

In order to test the capabilities of the shutter arrange- te ^P|^J**° { 
meut for standing the concussion of heavy guns fired in its ■ b wttey-aignai ing 

° ° ° and finng-appa- 

vicinity, experiments were tried at Sheerness with a working ratua during con- 

u ' A cussion produced 

model constructed on the principles above described. It by firing gun B . 
was placed on the parapet of the work, at a few yards dis- 
tance, during artillery practice with a seven-inch muzzle- 
loading rifled gun ; subsequently advanced close to the 
muzzle of the gun, and finally placed on the gun platform, 
and the only case in which the shutter fell was when the 
whole apparatus was knocked over by the recoil of the gun. 
The instrument was made to work by closing the circuit 
electrically between each round, in order to ascertain that 
its stability was not caused by any undue tension of the 
regulating spring. 

It would seem therefore that, with moderate care, there 
would be no danger of a shutter dropping by concussion, 
but experience has proved that it is necessary to balance 
the force of attraction, exercised by the electro- magnet, 
against the mechanical effect of the spring, with some degree 
of nicety, as in guarding against an accident due to the 
falling of a shutter, one is sometimes apt to apply the spring 
too strongly. 

Several modifications of the shutter signaling apparatus 
have been made, but before any one of them can be consid- 
ered sufficiently perfect to be received into the service, fur- 
ther experiments to determine their action when subjected 
to the effect of concussion, produced by the firing of heavy 
guns, must be made. Though the experiments tried at 
Sheerness were sufficiently conclusive as to the particular 
specimen tested, it is necessary that the instrument should 
be thoroughly tried under every possible condition which 
might occur in actual work. The stability of the shutter is 
a point vitally essential to its use, as in many instances it 
would be impossible to put it in such a position as to be out 
of reach of concussion. The question of the stability or 
instability of the shutter involves a condition of balance 
between the force exerted by the regulating spring pulling 
the armature in one direction, and the attraction of the 
electro-magnet acting in the opposite direction. In the 
circuit- closing system the spring must hold the armature 
sufficiently firmly to prevent the accidental fall of the shut- 
ter by concussion, while the battery must be so constituted 
as to act effectually when the circuit is closed. In the cir- 
cuit-breaking system the battery must, on the contrary, 



S h ut tor-signal- 



230 

hold the armature steady, while the spring ought to be able 
to act with sufficient force the moment the circuit is broken. 
It is not desirable to draw absolutely definite conclusions 
from the single experiment referred to, even though it was 
a very severe one on the instrument, and the conditions 
were infinitely less favorable than those which would ever 
occur on service. 

When the circuit-breaking svstem is used with the shutter- 



ty stain . 



cifc a ui*t™reaki f ng s ^S lia ^ n S apparatus, the action of the armature in releas- 
ing the lever must be reversed ; that is to say, that when 
the current is passing and the armature attracted to the 
horns of the electro-magnet, the shutter must be held up, 
and when the current ceases and the armature is drawn 
back by the action of the spring, it must release the lever 
and allow the shutter to fall. This is done by the arrange- 
ment shown in Fig. 95. The extremity of the lever (/) is 
bent up and passes round and under a projection (#,) at- 
tached to the lower portion of the armature (a;) when, 

Fig. 95. 




therefore, the current ceases for a moment and the arma- 
ture falls back, carrying the projection (g) with it, the lever 
(/) is detached and the shutter becomes free to fall. The 
projection (g) and the extremity of the lever (/) are made 
wedge-form, in order the more readily to become discon- 
nected from each other when the apparatus is put in action. 
Another form of shutter-signaling apparatus, designed 



231 

for use with a circuit breaker, is shown in Fig. 96. Iu this s hutter signal - 
instrument the shutter (a) is pivoted on a metal axis (b) with ™fth BtrSt™™ 
two projections, insulated as before, with ebonite. The elec- tromagnet - 
tro-magnet (e) is, in this case, composed of a single coil, and 
two levers, (d) and (d',) one attached to each extremity of 




~ ] J (i )Galuariom££&r 

*«^D-H|i|i|ilil - ! • — ilililil — o&*^ 

Su/naZ&ng Battery Testing BcUCery 

D-H|l|ilil"l«li|ililill|l|ili|il".l- 

Firing BaJtery 



the axis (6) on which the shutter is pivoted, are so arranged 
that they may be attracted to and held by the electro-mag- 
net as long as the current is passing, id) being held by the 
front and (d f ) by the rear point of the electro-magnet. A 
small capstan-headed screw (h) regulates the distance be- 



tween the 



electro-magnet and 



the' armature; it prevents 



232 

absolute contact, which might be detrimental in the case of 
residual magnetism, and by it the sensitiveness of the appa- 
ratus may be regulated. When the current ceases the shut- 
ter falls down into the position shown by the dotted lines, 
and, the springs and connections being precisely similar to 
those already described, the firing-battery is thrown into 
circuit as before. Fig. 96 shows the connections of the 
apparatus; (/) is the terminal to which the firing-battery 
must be attached, [g) the terminal for the testing-battery 
and galvanometer, (c) the terminal for the signaling-bat- 
tery, and (/,) for the electric cable to connect the fuse in the 
charge. A plug (p) provides the means of rapidly detaching 
the firing-battery; this latter is entirely out of circuit, and 
no mine in connection with the group can be fired unless 
the plug (p) is inserted between the two brass plates pro- 
vided for it. A second plug is used to connect the signal- 
ing-battery by insertion between the brass plates provided 
for that purpose; if removed from (q) and inserted at the 
point (r,) the signaling-battery is cut off from the circuit 
and the testing-battery is thrown in. When the ping (q) is 
taken out for testing purposes there would, of course, be a 
cessation of current through the coils of the electro-magnet, 
and the shutter would fall down and complete the circuit of 
the firing-battery ; to guard against such an accident it 
would be necessary, therefore, when testing, previously to 
remove the plug (p.) 

W T ith the exception of the action of the electro-magnet in 
dropping the shutter being the reverse of that previously 
described, that is to say, dependent upon the cessation of 
the current and not on its action, the mode of operation of 
this apparatus is precisely similar to that already given, and 
need not therefore be agaiu described. 
shutter signal- Another form of this instrument is shown in Fig. 97. Its 
whhmer P cur y a con S armature, electro-magnet, regulating spring, stud, shutter, 
motions. an( j a tt a ched lever are precisely similar to those first de- 

scribed, (see page 226,) but the connections are made by 
two mercury cups, (a) and (&.) When the lever is horizontal 
and the shutter drawn up and ready for action, the circuit 
of the signaling-battery is completed through the mercury- 
cup (a,) along an arm (c) projecting downward from the 
lever (d,) and thence to the shutter-pivot and line terminal 
as before. When the shutter is down, as shown by the 
dotted lines, another arm, (e,) a prolongation of the lever (d,) 
falls into the mercury cup (c,) which latter is permanently 
connected with the firing-battery. The object of the mer- 
cury-cups is to get rid of the springs in the original design, 



F-- 9 . 97. 




•i 






— Hl|l|l|l|l|l|l|H 

JFiriny Battery 



233 



electrical circuits, dependent on the pressure of spring, being 
always liable to interruption from dirt or oxide intervening 
between the points of contact. There would be much less 
danger of such a contingency if mercury-cups were used. 
Fig. 98 shows a plan of the apparatus ; (fb) is the firing-battery 

Fig. 98. 




-~o-- 1 - 


i ■ -?' _215:^li_ 


i 

i -. 

V 

\ 




\ 
/ 


"r^-^r * 


i 



Belt 



terminal, (s b) the signaling-battery, terminal, and (g) the 
testing-battery and galvanometer terminal. These are con- 



234 

nected with brass plates, as shown by the dotted lines, and 
plugs are provided, as before, for altering the connections. 
There is an electrical bell in the firing circuit to give notice 
by striking when a mine has been fired. 
ing hu "ppSus The sh utter- signaling apparatus maybe so arranged as 
ing\eyl w " r to be worked on the circuit-closing system, by a combination 
of firing-keys, in connection with observant stations, in any 
of the systems described at page 186, and those following, 
(Figs. 78, 79, and 80.) It would only be necessary to con- 
nect a battery of similar constitution to the signaling- battery, 
so that its circuit might be closed and current passed 
through the coils of the electro-magnet of tlie shutter appa- 
ratus, by means of the depression of firing-keys, and the 
shutter, corresponding to the particular mine to be fired, 
would thus be released at the proper moment and the firing 
battery thrown in. In this way a system might readily be 
used, if required, for firing by intersection when the posi- 
tion of the mines are distinctly visible, while a simple 
change of connections would render itself acting at very 
short notice. 

Should the circuit-breaking system be used, the combi- 
nation would not be so simple. The visual circuit-closing 
system is dependent, in two out of three of the cases described, 
(Figs. 78 and 80,) on the closing of the circuit at two dis- 
tinct points, while the breaking of the circuit at one point 
would cause the* shutter to fall. If, therefore, a circuit- 
breaking combination were used, it would be necessary to 
arrange an entirely separate system on the circuit-closing 
principle for signaling j in this way the number of a mine 
might be readily indicated to an operator, and he might 
throw down the shutter by hand. 

If a system of firing by intersection, combined in this 
way with a self-acting system, were used, the observing- 
stations would frequently be some distance from the testing- 
room; they (theobserving-stations) ought to be, if possible, 
w T ell clear of the smoke of guns in action, while the testing- 
room ought to be within a fort and in a bomb-proof case- 
mate, well covered from an enemy's direct and vertical fire. 
It ought not, in point of fact, to present any opening in the 
direction of the enemy's guns. There would, however, be 
no difficulty in arranging a combined system under such 
conditions, either for the circuit closing or breaking system. 
Arrangement of The shutter-signaling apparatus may be conveniently 

shutter-signaling , . , ,. --i i i • ' j_ • >i 

apparatus in box. arranged in a compact form, with a long box to contain the 
coils, which box should be made to shut up and lock, to 
prevent interference by unauthorized persons. The battery 



Fig. 99. 




235 

terminals, brass plates, plugs, &c, should be placed ou a 
board in front and outside the box itself, so as to be acces- 
sible at all times. The coils of the electro-magnets may be 
conveniently placed side by side: in this way six coils, 
with their necessary terminals, brass connecting-plates, &c, 
would occupy a space of 30 inches in length, 9 inches in 
breadth, and 7 inches in height. The bell would stand 6 
inches high over the top of the center of the box. 

A form of testing and firing table has been designed in . wooimch-test- 

00 ° ing and firing ta 

the chemical department, Woolwich, adapted for a self-acting ble - 
system of mines, the general arrangement of which is shown 
in Fig. 99. The electric cables, in connection with the 
mines, having been brought into the fort, are each attached 
to a series of screw-plugs, inserted into perforated metal 
plates insulated by ebonite rings (a a a, &c.,) which latter 
are numbered to correspond with the number of the mine 
or system of mines to which each belongs. A second series 
of screw-plugs (b b &, &c.,) in metallic connection with (a a 
a, &c.,) is arranged to receive a series of insulated wires, 
connecting the electric cables with a metal plate (c,) by 
means of a series of binding-screws (d d d, &c.) This metal 
plate (c) is permanently counected with the firin g- battery ; 
if, therefore, a vessel were to strike one of the circuit-closers 
of the system, the circuit of the firing-battery would be 
completed through the fuse and the fuse would be fired. 
The positive (copper or carbon) pole of the firing-battery is 
connected with the plate (p,) containing three holes for 
screw-plugs, which are brought into metallic connection by 
it; the negative (zinc) pole of the battery is connected with 
a similar plate (n.) Another insulated plate (e,) made to 
receive three plugs, the center one of which is connected to 
earth, is placed in a convenient position on the table to 
facilitate such changes of connection as may be required 
in using the apparatus ; three holes are supplied in each 
case, so that one or more connections may be made at each 
of the poiuts (p n e) if required, as it may be necessary to 
use more than one such connection at a time in testing the 
condition of the lines. When arranged for action, the posi- 
tive pole {p) of the firing-battery is connected to (e,) and the 
negative pole (n) to the plate (c,) as shown by the dotted lines. 
The positive (copper) pole of the testing-battery is connected 
by means of a screw-plug with the plate (p',) and the negative 
(zinc) pole with the plate (n' ? ) two other screw-plugs in each 
case being, as before, disposable for an}' required connec- 
tions. Another insulated plate (g) is in connection with one 
binding-screw of an astatic galvanometer (g') placed in a 



236 

convenient position on the table, while an insulated wire, (?,) 
long enough to reach to any one of the screw-plugs of the 
combination, is attached to the other terminal of the galva- 
nometer. The positive pole ($>') of the testing-battery is 
permanently connected for work with one of the earth ter- 
minals at (e,) while the negative pole (n') is connected with 
one of the terminals at (g.) The whole object of these nu- 
merous binding-screws is to give facility for changing the 
several circuits with the least possible delay. 

use m testing. In order to test any one of the electric cables for insula- 
tion, conductivity, or for any other purpose, it would only 
be necessary to disconnect it for the time from the firing 
circuit, by removing the connection between the screw-plug 
(b) and the plate (c,) and to insert in its place the wire (/;) 
the testing-battery would thus be put in the circuit, through 
the galvanometer, with the particular line to be operated 
upon, and its efficiency as regards insulation, conductivity, 
&c, indicated by the movement of the needle of the instru. 
nient. 

Arrangements To test the condition of the firing-battery, Mr. Abel pro- 
b°a r t<ery. ing finng ' poses to use a small set of resistance-coils in connection 
with a thermo-galvanometer or bridge, in which he proposes 
to place a definite short length of fine platinum wire of known 
electrical resistance. The working power of the battery 
would be tested by the fusion of the thin platinum wire 
through a given electrical resistance, as indicated by resist- 
ance coils put in circuit, and a practical test of its efficiency 
would thus be obtained with great facility. This test would 
of course only be applicable in the case of a battery pos- 
sessing the power to fuse a fine platinum wire, and it would 
be necessary actually to fuse and not to simply heat the 
wire more or less red, in order to obtain definite knowledge 
concerning the battery, as previous to actual fusion no defi- 
nite information as to the degree of heat produced by the 
battery could be obtained by this means, as a measure of 
its working powers. To test a battery which would not 
fuse a short length of fine platinum wire, some other means 
must be adopted, but the same kind of information might be 
obtained by firing an ordinary tension fuse, of known resist- 
ance and through a known resistance as indicated by the re- 
sistance-coils. The battery power required to fire a tension 
fuse would not perhaps be determined within such small lim- 
its as that necessary to fuse the platinum wire, but it would 
answer perfectly well for practical purposes. Whether the 
platinum or tension fuse were employed, it would not do to 
rely on the results of such an experiment to determine abso- 



237 

lately the number of battery-cells to be used in practice. 
If a certain number of cells, tried in this way, just fired the 
fuse through a resistance equivalent to that of the electric 
cable, &c, it would be desirable in practice to double that 
number of cells. It must be remembered that the condi- 
tions in the experiment are always far more perfect as 
regards insulations, &c, than can ever occur in practice, 
where all sorts of deteriorating influences must necessarily 
exist to mar, at least in a degree, the perfection of the 
combination. 

The resistance coils and connections for this test must be wire of coiis 
suited to the nature of the firing-battery used, for example, Kter/cSrent. ° 
thick wires in the resistance coils if a quantity battery is 
employed, and fine for a battery of high electromotive force. 
The whole might be arranged in any convenient position on 
the testing-table. 

Tt is also proposed to provide the testing- table with a 
commutator, by which means the number of battery-cells 
used for testing purposes may be rapidly and conveniently 
altered. 



CHAPTER XIII. 

MECHANICAL AND ELECTRICAL TESTS. 

Having now given a general description of the arrange- 
ments which seem to be best suited for working out any 
system of defense by submarine mines, it only remains to 
explain how the several component parts of the system may 
be put in proper practical working order and kept so after 
submersion. 

Tests employed. To insure this it becomes necessary to test the different 
component parts of the system carefully before they are 
placed in position, and to retain the power of ascertaining 
their efficiency, as far as possible, at any period after they 
have been combined and put in the water. The tests em- 
ployed are of two kinds, mechanical and electrical. 

Mechanical tests. Mechanical tests should be applied to ascertain that the 
mechanical arrangements of the shutter apparatus, circuit- 
closers, and all similar appliances work easily and efficiently ; 
that the several parts of the case to contain the charge, 
when put together complete, are water-tight ; and that it is 
sufficiently strong to bear the external pressure due to the 
depth at which it is to be submerged, for a considerable 
time without leaking. 

Electrical tests. Electrical tests are those which must be applied to the 
several component parts of the system to ascertain that the 
electrical conditions, necessary to a successful result, exist ; 
for example, that the electric cable possesses a sufficient 
amount of insulation and conductivity; that the firing-bat- 
tery is in such order as to insure certain ignition; that the 
electrical connections of the circuit-closers are correct, and 
other similar information. By means of certain electrical 
tests we can also ascertain after immersion, with a consid- 
erable degree of certainty, whether the several combinations 
of a system are in such a condition that it will work effi- 
ciently. This is a very important fact; for the whole 
thought, trouble, and previous preparation bestowed on a 
submarine mine is undertaken in order that it may act effi- 
ciently at a single instant of time, and it becomes valueless 
unless it does so act without failure. 
Tests before and Each portion of the apparatus should be tested separately, 

ifter submersion. \ . . *; V . , . , ' . 

and combined m the form in which it is to be used before 
submersion, and the whole should be again tested immedi- 
ately after submersion. 



239 

As a preliminary to all electrical testing it is necessary to Tests of instm- 
ascertain that the instruments, batteries, &c, used in making 
the tests, are themselves in good working order, otherwise 
defects which exist in the testing instruments may produce 
results which might be mistaken for defects in the apparatus 
under trial ; for example, a want of proper connection in the 
construction of a, galvanometer might be mistaken for want 
of conductivity in an electric cable, or for a high condition 
of insulation which might not exist. 

The following modes of testing the several component 
parts of the system may be adopted : 

The explosive used would be either gunpowder, cun-eot- . Testa of ex P lQ - 
ton, or some similar compound ; as a general rule these 
might be accepted as of good quality, but should any sus- 
picious appearances present themselves, or should facilities 
be at hand, tests should be made. Gunpowder may be 
tested by an eprouvette, or by firing small charges out of a 
mortar and measuring the range obtained. Gun-cotton may 
be tested chemically, or practically, to see that it possesses 
detonating qualities. Any other explosive of a similar 
nature could be tested in a similar manner. 

The case to contain the charge should be tested to ascer- Testa of case. 
tain that it is thoroughly water-tight, and capable of bear- 
ing external pressure to the extent required, according to 
the depth at which it is to be submerged. This test may 
be applied by forcing in water by means of a hydraulic 
press, to any given pressure, and observing the joints, &c, 
to see that nothing comes through them or through the 
body of the plates themselves. This should be clone during 
the process of manufacture, and the leaks at the joints, 
should any exist, should then and there be calked. Any 
leak through the body of the metal itself would necessitate 
the rejection of the entire case. Gases of J-inch boiler- 
plate iron should bear a pressure from within of forty 
pounds on the square inch without a suspicion of leak. To 
test for capacity to bear external pressure, the cases, having 
first been made complete with mouth-piece, &c, to close 
the loading-hole, as for service, may be submerged to a 
depth somewhat exceeding that at which they are eventu- 
ally to be used. After remaining thus submerged for not 
less than forty-eight hours, they should be lifted, opened, 
and carefully examined, to see that they remain perfectly 
dry inside. In making this examination it would be neces- 
sary, in the event of damp having penetrated, to ascertain 
whether it had forced its way in at the junction of the 
mouth-piece, or through the joints or metal plates composing 



240 

the body of the case. No electrical test can be applied as 
far as the simple metal is concerned; when complete, how- 
ever, with month-piece, fuse, &c, before submersion an 
electrical test, to be hereafter described, should be applied 
to ascertain the condition of the apparatus as a whole. 
Tests of xuoor- AH mooring apparatus should be tested mechanically ; 

ing apparatus. . . 

first, to ascertain that the weights of anchors or sinkers are 
such, considering the buoyancy of the case, rate of current 
in which it is to be moored, and nature of bottom or holding 
ground, as to keep the mine in its proper position after sub- 
mersion. Second, the chains, wire cables, and ropes to be 
employed should be examined to see that they are of sound 
construction ; and, if the slightest doubt exists as to their 
quality, they should be further tested mechanically, by 
applying a strain of a measureable nature, to ascertain 
whether they are fit to perform the work required. No 
electrical tests are applicable to this part of the apparatus. 

Tests of me- Mechanical fuses, such as the sulphuric acid fuse, &c, 
might often be improvised and should be practically tested 
in course of construction. A fuse of this nature which may 
at any future time be made an article of store, to be drawn 
out as required for use, must be tested practically, by selecting 
a certain percentage of those issued and firing them ; should 
the results be good the whole may be accepted as of good 
quality; if failures to fire occurred they would indicate more 
or less deterioration or imperfection in the whole. Abel's 
torpedo primers should be tested in this way. Mechanical 
fuses cannot be tested electrically. 

Tests of piati- The platinum wire fuse may be very simply tested electri- 
coodilctivity' 6 for cally. If placed in circuit with a few cells of a battery (c z,) 

Fig. 100. 




ra 



and a common detector galvanometer (#,) as shown in Fig. 
100, before the fine platinum wire (p) is soldered across 
between the wire points there should be no deflection of the 
needle, for no metallic circuit should exist; if it did it would 
be fatal to the efficiency of the fuse. If placed in circuit 



241 



101. 



with the same battery and galvanometer, after the hue pla- 
tinum wire had been connected to the extremities of the larger 
wire points, a considerable deflection of the needle should re- 
sult, such deflection being due to the current passing through 
the platinum wire bridge, which, to be efficient, ought to be 
the sole medium through which the circuit is completed. 
This test should be made with a few cells of Darnell's, or 
other similarly constituted battery, the current generated 
by this form of battery being of such a nature that no sen- 
sible heat would be produced in the platinum wire, and no 
chance of an explosion of the fuse incurred. This is espe- 
cially necessary in testing the fuse after it has been placed 
in the charge, when a premature explosion would of course 
be a very serious matter. The current of Grove's, or other 
battery, so constituted as to fire a platinum fuse, would 
moreover injure, if not destroy, the coils of the galvanome- 
ter unless specially constructed for use with it, and should 
never be thus employed: The continuity of a platinum wire 
fuse may also be tested by means of a water-decomposer, 
as shown in Fig. 101. The passage of the electric current 
through the water would decompose it, and 
hydrogen bubbles would be deposited on 
the point in connection with the negative 
pole of the battery. Should a want of 
continuity exist in the fuse, no current 
would pass and no water would be decom- 
posed. The apparatus consists simply of 
a glass bottle (a) to contain the liquid, 
into which a pair of wires, (&. &,) insulated 
from each other, have; been introduced, 
by simply passing them through a cork. 
A single cell of Grove's, or any battery 
by which a platinum wire may be fused, 
may be used in testing for continuity with 
this apparatus, provided the insulation 
between the wires passing into the bottle is sufficiently good, 
and the space between them, within the bottle, is sufficiently 
great to obviate the chance of premature explosion. In 
testing with a Grove's cell, extreme care is necessary to pre- 
vent the accidental closing of the circuit directly through 
the fuse by bringing the terminals in contact with each 
other, without the intervention of the resistance of the 
liquid in the bottle ; in order to guard against this the wire 
terminals, outside the bottle, should be bent well apart. 
Salt, or acidulated, water is better than fresh for testing 
16 




242 



purposes, as exhibiting the effect of its decomposition more 
rapidly. 
ance 8 of °piatSuui The electrical resistance of a platinum wire fuse may be 
wire fuse. ascertained by balancing, by means of a set of resistance- 

coils (r) and a deferential galvanometer (g.) Any number 
of Daniell's cells required may be used for this operation, 
but, for the reasons already given, Grove's battery is inad- 
missible for such a purpose. Fig. 102 shows the connec- 
tions to be employed for a test of this nature. The resist- 

Fig. 102. 



bKd 



il|l|l|l|l|l^-A 



ance of the coils is adjusted, by taking out plugs till tlie 
needle of the galvanometer is brought to zero, when the 
sum of the resistances indicated by the unplugged coils will 
, be equal to that of the fuse. The electrical resistance of 
T y of fine platinum wire, weighing 1.9 grains to the yard, 
is T 8 o of a B. A. unit nearly, (Schaw ;) this is its resistance 
at the moment of fusion. The resistance of T y, obtained 
by balancing with a set of resistance-coils, as in Fig. 102, 
is about T 2 o of a B. A. unit ; t 3 q 7/ is a good length of wire to 
employ as a fuse, and may be adopted as a standard. 
Tests of high- Fuses adapted to be fired by electricity of high tension, 
conductivity^ 01 such for example as Abel's fuse, require much more careful 
and delicate management in order to test them ; they may, 
however, be tested for conductivity and resistance, and this 
must always be done before they are used in any operations 
connected with submarine mines, to insure the maximum of 
efficiency at the proper moment. The test for conductivity 
must be made with a few Daniell's or other similar batten 
cells of small surface, adapted for tests of this nature, and 
an astatic galvanometer. The high electrical resistance of 
fuses of this nature, amounting in the case of Abel's fuse to 
as much as 1,500 or 2,000 B. A. units of resistance, combined 
with the danger of premature explosion when testing with 
even a small number of battery cells, renders it necessary 
to employ the astatic galvanometer, on which, in consequence 
of its greatly superior sensitiveness, a deflection is produced 



243 

by a comparatively small current. A reflecting galvanom- 
eter would of course be preferable for such work, but is 
much more expensive and not a very portable instrument. 
The resistance of a high-tension fuse may be obtained in Test " °* ™ s } at " 

v ance of high-tcn- 

couuection with a differential galvanometer, by balancing sionfuses - 
by means of a set of resistance-coils, as in the case of the 
platinum wire fuse. For the reasons already given, a 
very moderate battery power must be employed, and 
a more sensitive galvanometer used in this operation. The 
resistance of this form of fuse may be very accurately 
determined by means of Wheatstohe's bridge and a re- 
flecting galvanometer. For general work, however, an 
astatic galvanometer will give results sufficient for all 
practical purposes. The precautions necessary in testing 
Abel's fuse are given at pages 94 to 96, and these must be 
adopted generally in testing high-tension fuses of any form. 

The tests to be employed for detonating fuses would be Tests of detona- 
precisely similar to those for ordinary fuses of the same con- ting fuses ' 
struction, the only difference being in the priming, (fulmin- 
ate of mercury instead of gunpowder.) They should, 
however, be subjected to a further test to ascertain that 
their detonating properties are sufficient to insure success; 
a deficiency of detonating conrposition will often produce 
imperfect detonation in the explosive itself, when used with 
compressed gun-cotton. A percentage should, therefore, 
be tried to ascertain their efficiency in this respect. 

Each fuse should be tested before and after it is placed 
in the charge, subsequently as a part of the general combina- 
tion in whichitisto be submerged, and finally, directly it has 
been placed in position for work. Any change in the results 
obtained by the first and subsequent tests applied would 
indicate a change in the electrical conditions, as well as give 
such information as would indicate efficiency or otherwise 
of the system, as will be hereafter explained. 

It is, perhaps, almost unnecessary to test electric cables, Tests of electric 
suitable for submarine mining purposes, mechanically 'for aTt^ti Mecha,nc " 
tensile strength ; extraordinary precautions are taken by 
giving them strong outer protecting covering of iron wire, • 
hemp, &c, intended not only to give tensile strength but to 
protect them from injury by rubbing against rocks, &c. 
Special precautions too are employed to prevent any great 
strain being brought to bear upon them, either during or 
subsequent to submersion. Should, however, any doubt 
arise as the ability of a cable to sustain a strain likely to 
be put upon it, it may be tested for tensile strength in the 
same manner as an ordinary rope. When an improvised 



244 



electric cable is employed it would always be advisable to 
ascertain its tensile strength before putting it to practical 
use. 
insulation test Electric cables should be tested electrically for insula- 

for electric cables. ^ 

tion, conductivity, and electrical resistance. To test for 
insulation the cable should be put in a tank of water and 
allowed to soak for 48 hours. The object of this soaking is 
allow the water to penetrate through the outer protect- 
ing covering of .hemp and iron wires, and to search out and 
get into auy weak places there may be in the insulation. 
After soaking, one end (a) of it should be reconnected, as 
shown in Fig. 103, with an astatic galvanometer (#,) and 



Fig. 103 








! Illlllllllltl 



battery (c z) of not less than 50 DanielPs cells, while the other 
end (b) should be carefully insulated. The battery circuit 
should be completed by an earth-plate (e) in the tank (t) 
through the galvanometer (#,) and the deflection of the latter 
should be observed. It is manifest that in such a combination 
any current, passing through and deflecting the galvanome- 
ter, could only complete the circuit by passing through the 
insulation of the cable. A very slight deflection would fre- 
quently be observed on a moderately sensitive galvanome- 
ter in such a combination as that indicated in the figure, 
even with a well insulated cable. This would be due to the 
current passing through the insulation ; its whole length 
being immersed, the surface through which such a current 
would pass would be large, and the sum of the infinitesi- 
mally small quantities, escaping over the whole length, 
would, in the aggregate, be sufficient to deflect the galvan- 
ometer to a small extent in completing the circuit of the 



245 

battery. Should any considerable deflection occur, it 
would indicate a defect, or leak, in the insulation of the 
cable, the extent of which would be roughly measured by 
the amount of such deflection. In making a test of this 
nature a large number of battery-cells, at least 50, and, if 
possible, more should be used, the object being to obtain 
high electro-motive force to drive the current through auy 
defects which may exist. The battery-current should not 
be kept circulating longer than necessary during a test of 
this nature, and in order to close and break the circuit with 
facility, it would be convenient to insert a manipulating 
key, (I;) Fig. 103, in the combination. Should a leak exist 
in the cable, the effect of the continuous passage of 
electricity would be to polarize that leak, and thus to intro- 
duce a conflicting element into the combination which 
would be likely to interfere with the value of the test. If 
the tank in which the cable was coiled away were of iron 
or other metal, the earth-plate (e) might be dispensed with, 
and the circuit simply connected by a wire to the tank 
itself. When no tank is available an electric cable may, for 
testing purposes, be immersed in the sea or in any water, 
and equally good information obtained by testing it in the 
manner described. 

Having completed the test for insulation, an electric Test of electric 
cable should next be tested for conductivity. To do this it 5Uy! 
would only be necessary to remove the insulation from the 
end (&,) Fig. 103, of the cable, so as to expose the metallic 
conductor, and put it in the water of the tank. If the con- 
ductivity were good, the whole of the battery-current would 
then pass through the cable, and the galvanometer would 
be violently deflected. If the continuity were broken no 
deflection of the galvanometer would occur. 

Very much more delicate tests for insulation might be 
obtained by substituting a reflecting for an astatic galvan- 
ometer, but for the comparatively short lengths of electric 
cable required for use in submarine mining operations, such 
minute accuracy is seldom necessary, though, at important 
stations, the more delicate apparatus might be very usefully 
employed. 

It must be borne in mind, however, that whatever instru- sensitive gai- 

1 ' variometers best 

ment is used, the deflection of a galvanometer only conveys a for testiu s- p ui ' 
comparative idea of a current passing through its coils. A 
current which would produce absolutely no motion on an 
insensitive galvanometer, would cause a considerable deflec- 
tion in the needle of even a moderately sensitive instru- 
ment. An operator should, therefore, know the nature of • 



246 

the instrument with, which he is working, and it is prefera- 
ble for hitn to employ a tolerably sensitive instrument, with 
the use of which he is thoroughly acquainted, than a rough 
one with which the more delicate observations could not be 
made. 
Negative cur- The negative (zinc) pole of a batterv should always be 

rent best for test- o \ / z J j 

mg purposes. attached to a table for testing purposes, because if the 
positive (copper) pole were attached, a salt of the metal of 
which the conductor was formed would be immediately de- 
posited in any defect which might exist in the insulation if 
the metallic conductor were in the slightest degree exposed. 
This would occur in any water, unless absolutely free from 
impurities, and would be especially the case in salt water, 
in which a chloride of the metal would be quickly formed. 
This would almost immediately insulate the defect to a 
certain extent, and a true deflection would not be obtained 
on the galvanometer. The effect of a negative current 
would be to decompose any such salt and to deposit the 
metallic component on the conductor, and thus, so to speak, 
to clear the defect and expose a purely metallic surface at 
the point required. 

Tests for rauiti- To test a multiple cable for insulation and conductivity, 
a similar course should be pursued with each conductor as 
has been described for a single cable. In testing each 
single core, the conductors of all the others should be put 
to earth to obviate the effect of induction which would, 
more or less, according to the length of the cable, interfere 
with the results of the observations obtained. 

to discover po- Should a defect in insulation be indicated by the tests 

sition of a defect . . 

of insulation. above described, its position might be readily ascertained, 
by keeping a continuous current on from the battery, and 
gradually taking the cable out of the tank. If the imper- 
fection existed at a single point, the defection of the gal- 
vanometer would be suddenly much reduced at the moment 
the defect was raised out of the water, and its position 
would thus be determined with considerable accuracy. 
Should several defects exist, as each was lifted out, a sud- 
den reduction of deflection would occur. 
Discharge test. Want of continuity in an electric cable may co-exist with 
perfect insulation ; for example, the conductor might be 
parted within the insulation, while the latter remained good. 
Under such circumstances the tests above described would 
indicate good insulation but no conductivity, without giv- 
ing any information as to the position of the severance 
of the conductor. To ascertain this the following test may 
be applied: Having put one pole of a battery of 200 or 






247 

more DanieH's cells to earth, charge one eiicl of the defective 
cable, and immediately discharge through a reflecting gal- 
vanometer, noting the extreme limit of the swing of the needle, , 
then charge the other end of the cable in a similar manner, 
and discharge it through the same galvanometer, noting 
the swing of the needle as before. This should be done 
three or four times, and an average of the deflections taken. 
The position of the break in the conductor would be indi- 
cated by the proportion between the average deflections in 
each case, and the cable might safely be cut at the point 
so determined, which, if the tests Avere carefully made, would 
not be very far from the defect. Should the precise position 
of the fault not be discovered in thus cutting the cable, 
each section should then be again tested for conductivity, 
and that in which the fault was still found to exist should 
be again tested by the discharge as before. In this way the 
exact point would finally be discovered. 

The deflection of the needle is dependent upon the quan- 
tity of current, at a given potential discharged through the 
coils of the galvanometer, and the quantity is again depend- 
ent on the electrical capacity of the conductor of the 
cable to contain a charge forced into it at a given potential, 
and its electrical capacity is directly in proportion to its 
length, supposing the conductor to be of uniform size 
throughout. The swing of the galvanometer-needle meas- 
ures the quantity of the charge passed through its coils, in 
proportion to the sine of half the angle deflected, (Jenkin ;) 
hence on a reflecting galvanometer the information would 
be* given directly, in proportion to the number of divisions 
on the scale, as indicated by the extreme motion of the spot 
of light, while on the galvanometer reading the angular 
measure in degrees, &c, the sines of half the angles de- 
flected would give the required proportion. Few galvan- 
ometers, except the reflecting instrument, are sufficient^ 
sensitive to enable the " discharge-test" to be employed. 

After testing for insulation and conductivity, the electri- Test of electri- 
cal resistance of an'insulated cable should be measured, cable. 
This should be done by balancing it against a set of resist- 
ance-coils, in connection with a differential galvanometer, 
in a similar manner to that shown for the fuse in Fig. 102. 
The coils should be unplugged till its galvanometer-needle 
is brought to zero, when the sum of the unplugged coils 
would be equal to the electrical resistance of the cable. A 
more delicate test of this nature may be made by Wheat- 
stone's bridge and a reflecting galvanometer. The electrical 



248 

resistance of the conductor of a cable affords a very cor- 
rect indication of the quality of the metal of which it is 
composed. 

In making these tests DanielPs or some similar form of 
battery should be employed, so that the delicate coils of the 
galvanometers, &c., may not be injured. 
Mechanical tests Water-tight joints and connections should be tested 

ot water-tight ° 

joints. mechanically, by immersion, for not less than 48 hours, at 

depths somewhat greater than those at which they are to 
be eventually used, after which they should be raised, 
opened, and examined to see that they remain dry. 

ofSsuiatedjoinfs! Insulated joints and connections, whether of a permanent 
or temporary nature, should be tested electrically, in a 
precisely similar manner to that described for electric cables. 
They should be soaked for 48 hours and then tested for 
insulation, conductivity, and electrical resistance. 

In testing the permanent joints made in a line of subma- 
rine electric cable, special precautions are taken, which are 
described by Mr. Culley as follows: 

" A joint should insulate as well, or nearly as well, as an 
equal length of the perfect core, and the object of the test 
is to ascertain if this be the case. The leakage, even from 
a considerable length of good core, is too small to affect the 
galvanometer ; although the electricity which escapes mo- 
ment by moment cannot be measured, still, if it were possible 
to store up the loss during a minute and compel it to pass 
instantaneously through the coils, it would produce a sen- 
sible deflection. 
Delicate test of " In order to effect this, recourse is had to induction. « A 

apparatus. ' * metallic trough, sufficiently large to contain two or three 
feet of the core, is suspended by straps or rods of polished 
ebonite, two or three feet long. A small condenser is at- 
tached to increase its inductive capacity, and enable it to 
store up the electricity which may leak through the insula- 
tion. The testing-battery, of not less than 200 cells, is in- 
sulated in a similar manner, and all loss over the surface of 
the conducting wires is prevented by paring their ends, so 
as to expose a fresh clean surface, or even by coating them 
with hot parafifine. 
to test the ap- u To ascertain if the apparatus is sufficiently insulated, 
the trough and condenser are charged, and the swing of the 
needle, from an immediate discharge, noted. They are 
then recharged and left free for a time equal to that to be 
occupied by the test and again discharged. The difference 
in the swing shows the loss in the time, and should be very 
small. 



paratuB, 



249 

"The joint is placed in the trough, a negative current is 
applied to the cable, and the positive pole of the battery is 
connected to the outside coating of the condenser. Any 
leakage which may occur through the insulation is, by this 
arrangement, accumulated in the condenser, aud may be 
discharged through the galvanometer after any given inter- 
val. 

"It is possible to find how much is lost by deflective in- 
sulation during the joint-test itself; but as both core and joint 
are subjected to the same conditions, and the object is sim- 
ply to see if one insulates as well as the other, this precau- 
tion does not seem to be absolutely necessary. 

"To make the test. 1st. Place the joint in the trough— th f t ° e d s t° fraakin 
leave one end of the cable free ; connect the copper pole of 
the battery to the galvanometer j connect the other terminal 
of the galvanometer to the trough, and, finally, charge the 
cable by applying the zinc pole. 

" The charge within the cable acts inductively upon the 
natural electricity of the trough, the wire being in fact the 
inner, and the water the outer coating of a Leyden jar. A 
portion of the negative electricity of the water is set free, 
and an equal quantity of the positive is held fast or disguised 
by the negative charge within the cable. The free electricity 
is at once neutralized by the action of the battery ; if it 
were not so arranged, it would increase the apparent leakage 
from the cable, being of a similar sign. 

"The deflection or swing due to the discharge being in- 
stantaneous, it follows that if the needle remains deflected 
after the discharge, the joint is very bad or there is leakage 
over the surface of the insulation. The latter may be con- 
ducted to earth so as not to interfere with the test, by 
wrapping an earth wire round the core a few feet from the 
free end. 

"2d. Without disturbing the charge of either cable or 
trough, connect one coating of the condenser to the trough, 
the other coating to the positive pole of the battery, the 
zinc being to the cable as before. 

"Any negative electricity which may leak from the cable 
will now accumulate in the condenser. Allow one minute 
for this. 

"3d. Disconnect the condenser from the trough and bat- 
tery and discharge it through the galvanometer. If the 
trough and other parts of the apparatus have been well 
insulated, the swing will show the accumulated leakage from 
the portion of core under test. It is evident that these 
changes must be made by perfectly insulated keys and 
commutators. 



250 
Effect of iu due- ^ it often occurs, when there are several wires Id the 

iioa when several ' 

joints are Bimuita- cable, that the apparent leakage is greater froin the ioint 

neously tested. ' L l ° ° J 

which is first tested than from any of the other joints tested 
at the same time. This arises from the charge in the first 
wire acting upon the others inductively. The wires not 
under test should therefore be put to earth until they are 
wanted, and the condenser and trough should be perfectly 
discharged between each test. 

" It will be understood that the results are simply compara- 
tive, not absolute; all that the method effects is to show the 
difference between the insulation of a joint and that of any 
other part of the core. 

"This method somewhat differs from that ordinarily 
adopted. It is usual to put one pole of the battery to earth ; 
but in this case leakage takes place over the whole cable, 
however long it may be. By the plan described, the leak- 
age is confined to the part in the trough: the whole force of 
the battery is concentrated there and the apparent leakage 
exaggerated." 

Though such minute accuracy is not absolutely essential 
in the short lengths of electric cable used for submarine 
mining purposes, it must be borne in mind that the higher 
the condition of insulation, the greater will be the efficiency 
of the system, and the longer the line, the greater the neces- 
sity for perfection^ as far as it can possibly be attained. 
stoneV °expioder," All electrical instruments used for firing mines at will, 
andSiar^appa- such as Wheatstone's exploder, Siemens's dynamo-electrical 
machine, and the Austrian frictional machine, should be 
carefully examined and tested to see that their mechanical 
arrangements are in good working order. They should fur- 
ther be tested, with a fuse and known electrical resistance 
in circuit, to ascertain their power to fire that fuse with cer- 
tainty. If the electrical resistance in circuit is considerably 
greater, (say double,) than that through which they are 
required to work in practice, it may be assumed that they 
are in good order. The Austrian frictional machine has a 
special arrangement, by which its working condition may 
be ascertained, on short circuit, by the length of the spark 
passing across a given space on closing the circuit between 
the armatures of the condenser. 

Electrical batteries should be tested for potential, internal 
resistance, and electro-motive force. 

To test the potential of a battery, one pole should 
be put to earth, and the other to charge one pair of the 
quadrants of a reflecting electrometer; when this is done a 
certain deflection of the spot of light will be observed, 



Tests of batter 



For potentials. 



251 

and the amount of the deflection, as compared with that 
produced by a standard cell applied to the instrument in a 
similar manner, would give the relative value of the poten- 
tial of the battery. In making such observations it is neces- 
sary to take care that the condition of the electrometer, as 
regards charge in the Leyden jar, &c, is the same, while 
the deflections with the batteries under comparison are 
observed. The reflecting electrometer is not a very porta- 
ble instrument, and requires very careful and delicate ar- 
rangements in connection with it, and the beautifully minute 
and accurate information obtained by it is not absolutely 
essential to efficiency, in connection with the comparatively 
short lines of electric cable necessarily used for submarine 
mining purposes; its employment may therefore be limited 
to the more delicate observations necessary at important 
stations. 

The internal resistance of a battery maybe readily obtained res T s e t ance of e ™£ 
by means of a double shunt differential galvanometer and fJ/;J_° nnecti011s 
set of resistance-coils, as Recommended by Mr. Latimer 
Clark, in his book on electrical measurements in the follow- 
ing manner : 

u Connect the battery and a set of resistance-coils in cir- 
cuit between the terminals A and D, and insert plugs in the 
resistance coils so that they give no resistance ; insert plugs 
at A and C, and also both the shunt plugs at A and D. 
The battery current will now flow through one-half of the 
galvanometer circuit only, being, however, reduced to j^b 
of its amount by the shunt D : the deflection of the needle 
must be carefully read. The plug A must now be removed to 
B, which causes the battery current to flow through both 
halves of the galvanometer, (each being shunted.) The cir- 
cuit will now be as shown in Fig. 105, and the needle will, 
.of course, be deflected somewhat more than before. Now 
unplug the resistance-coils which are in circuit with the 
battery until the deflection of the needle is reduced to its 
original amount, and the resistances unplugged will be equal 
to the internal resistance of the battery. For example, 
assuming the resistance of the half coil to be ninety-nine 
ohms, and that of the shunt wire one ohm, the joint resist- 
ance of the two circuits will be : 

Galvauometerxshnut of 99xl=0 . 99ohm , 

Galvanometer -f shunt 99+1 
Suppose the resistance of the battery to be four ohms, the 
two together=1.99 ohms, and the current acts on the gal- 
vanometer needle through one-half of its circuit only; when 



252 

the second half of the galvanometer is thrown into circuit, 
by shifting the plug from A to B, the resistance becomes 
4.99 + 0.99=5.98, and therefore less current passes ; but, 
since it acts upon the needle through both coils instead of one, 
the deflection is greater than before. The resistance coils 
are now varied until the needle recedes to its original deflec- 

Bg. 104?. 




tion, which will necessitate the unplugging of a resistance 
of four ohms, making the total resistance now 5.98 -f- 4=9.98, 
which is exactly double the first resistance ; that is to say, 
in the one case we had a current acting upon one coil through 
4.99 ohms, and in the other case acting upon the two coils 
through 9.98 ohms, the deflecting power on the needle hav- 
ing been increased in the same ratio as the resistance." 

This measure is obtained in terms of B. A. units of elec- 
trical resistance, and is thus at once comparable with any 
other electrical resistance required. 



253 

The comparative electro motive force of a battery may be^ 6 ^-™ * 1 ^ 
determined by means of a differential galvanometer andtery.' 
set of resistance-coils, in a very simple manner. Fig. 104 
shows a diagram of a double-shunt differential galvanome- 
ter and the mode of finding the electro-motive force with 



fig. 105. 




•Res. Coils 



this instrument, as recommended by Mr. Latimer Clark, is 
as follows : 

"This can only be done relatively in terms of some other,, connections for 

XD.6 test, 

standard battery. The method is as follows : Determine 
the resistance of the standard and of the other cells 
to be measured ; insert the shunt-plugs at A and D, Fig. 
104, and also at and B, as in the former case, and join 
up the standard cell in circuit with a resistance-coil to the 
terminals A and D, and unplug the resistance-coils until a 
convenient deflection is obtained, say 15° ; note the sum of 
the resistances in circuit, including that of the battery, 
galvanometer, resistance-coil, and connecting wires; now 
change the cell for another, and by unplugging the resist- 
ance-coils bring the needle again to the same deflection, 15°; 
having again found the total resistance in circuit, the rela- 
tive electro-motive forces of the two cells will be directly 
proportional to these resistances." 

The electro-motive force thus determined is comparative ; 
that is to say, the result given by one battery may be com- 
pared with that obtained from another, and assuming any 
given cell as a standard, the value of each, as compared 
therewith, is obtainable. 

The electro-motive force and internal resistance of a bat- m ^\ forehand 
tery which is capable of fusing a fine platinum wire, may jj te ™ al " si sta " c t ® 
be found in the manner described in The Course of In- ter >- 



254 

struction in Military Engineering, page 140, paragraph 303, 
for Grove's battery. Mr. Abel proposes to fit up a simple 
arrangement of therino-galvanoineter and resistance-coils, 
suitable for this purpose, on his testing- table. (See page 
236.) 

Tests of system Having carefully tested the several parts of the appa- 
vvhoie. ratus, both mechanically and electrically in the manner de- 

scribed, they may be put together precisely in the combi- 
nation in which they are to be submerged. When elec- 
tricity is to be the igniting agent the system should be again 
tested electrically, as a whole, for insulation, conductivity, 
and electrical resistance. The results thus obtained would 
at once indicate whether the whole was in working order 
or not, and would be strictly comparable with the informa- 
tion obtained by similar tests, applied at any period after 
the mines had been submerged. A careful record should be 
kept of the results of all of the electrical tests applied, as 
by preserving the electrical history, so to speak, of any 
combination a defect in its electrical condition may be 
readily discovered, and the nature, position, and extent of 
such defect indicated with a considerable degree of certainty, 
without the necessity of raising the mine out of the water, 
or in any way disturbing the arrangements employed. 

rests after sub- After a mine has been submerged with electric cable, 
&c, complete, it should be immediately tested to ascertain 
that all is right, and similar tests should be applied at in- 
tervals to ascertain that the charge remains dry, and, in 
consequence, efficient; that the electrical resistance of the 
fuse is such as to indicate certainty of ignition ; that the 
insulation and conductivity of the electric cable remains 
good, and that its electrical resistance indicates a state of 
efficiency. The nature of the tests applied to ascertain these 
points depends upon the nature of the combination in which 
the mine is arranged ; that is to say, whether it is on a 
circuit closing or circuit-breaking system, whether the cir- 
cuit-closer is on a branch, or otherwise connected, and the 
nature of fuse used. The amount of accuracy with which 
the information, derived from electric tests, may be ob- 
tained, depends entirely upon the manner in which the 
several electrical circuits are connected up, and the nature 
of the tests to be applied must be determined accordingly. 

Test to ascertain The arrangements for testing to ascertain whether a 

that the charge is ° ° 

dry. charge is dry, at any period after submersion, are shown in 

Fig. 106. A plate of zinc is introduced at the point (a) 
within the charge, in connection with the conductor of the 
electric cable, and between the fuse and the shore, while a 



255 

plate of carbon (b) is connected with the electric cable, be- 
yond the fuse, to form the ordinary earth connection of the 
system at that point, and a copper earth-plate (c) is used at 
the home end of the cable. Taking advantage of the fact 
that if two plates, of suitable metal to form a voltaic bat- 
tery, are placed in salt water and connected by a metallic 
conductor, a battery is at once formed, capable of producing 

Fig. 106, 





i^L-..J 



considerable deflection on a moderately delicate galvan- 
ometer ; the combination shown in Fig. 106 has been made 
available for testing purposes. This arrangement has been 
termed the " sea-cell." The length of the conductor be- 
tween the plates is, within reasonable limits, (up to two or 
three miles,) no practical impediment to the action of the 
current set up, as far as the deflections produced on the 
needle are concerned. Let us suppose in the first instance 
that the charge is dry, and the insulation and conductivity 
of the cable good; under these circumstances we should 
have a sea-cell, composed of a copper and carbon pair, (c 
and &,) which would produce a deflection on a galvanome- 
ter (g) in circuit, in a certain direction, say from right to 
left. Suppose now that the charge had become wet by 
leakage through the case ; under these circumstances the 
zinc plate (a) would come in contact with the salt water, 
and a sea-cell, composed of a copper and zinc pair, would 
result ; this would give a different deflection on the galvan- 
ometer, and the needle would swing in the opposite direc- 
tion, or from left to right. This would at once indicate that 
the charge had become wet. 

Again, suppose that the insulation of the electric cable ina s u e SLf e caWe 
had become damaged to such an extent as to expose the 
copper conductor. Under these circumstances the sea-cell 
would be formed of two copper plates, one the permanent 
earth-plate, the other the exposed copper conductor, and a 



256 

certain definite deflection would be observed. This deflection 
would differ in character from that produced by the copper 
carbon sea-cell, which would exist under the conditions of 
good insulation, and would thus indicate a change in the 
electrical conditions of the combination, at the same time giv- 
ing such information as to lead to the supposition that an 
injury to the insulation of the cable had occurred. If the earth- 
plate at the home end of the cable were changed from copper 
to zinc, or to carbon, a fresh set of combinations would result 
giving different indications on the galvanometer, and these 
would provide the means of determining, with considerable 
accuracy, the reason for the change in the electrical condi- 
tions of the combination which they indicated. In this way 
the fact that a leak existed in the insulation of a cable might 
be discovered. Its extent and position might subsequently be 
approximately ascertained by tests to be hereafter described. 
sea-ceii test for Should the conductor of an electric cable be fractured 

continuity. 

within the insulation without injury to the latter, the fact 
would be ascertained by the sea-cell test. In such a case 
the continuity of the conductor being destroyed no deflec- 
tion on the galvanometer would result. Want of conduc- 
tivity or inefficient connections in the fuse would be simi- 
larly indicated. 
Disturbing in- In testing in this manner with the sea-cell, certain dis- 
test. e turbing influences occur, which must be obviated as far as 

possible. For example, the carbon earth-plate (b) beyond 
the charge becomes polarized, and acts in opposition to the 
current produced by the copper-carbon sea-cell ; in order to 
obviate this it is necessary to depolarize the system, by the 
application of a short current of opposite sign from a few 
cells of a voltaic battery, to bring the plate to what may be 
termed a neutral state, under which circumstances alone it 
is in a condition to give a correct deflection on the galva- 
nometer. The exposed metallic conductor of an electric 
cable becomes similarly polarized when subjected to the 
passage of a continuous battery current, and it must be 
depolarized by similar means. The polarization of the car- 
bon plates of any voltaic battery, into the composition of 
which this metal enters, is very rapid. The moment the 
battery-circuit is cl sed, the carbon plates become polarized, 
and much care and dexterity is required to depolarize them, 
when making the test for the internal resistance of the bat- 
tery, as described at page 251. Unless they are carefully 
depolarized, the internal resistance of the battery, found in 
this manner, will appear to be very much larger than it 
really is. It will be, in fact, the resistance after the current 



257 

has circulated, and not the resistance when the battery cir- 
cuit is first closed. 

The following demonstration of the general principle on 
which the liquid resistance of a battery is calculated by the 
differential galvanometer, shows that the result found by 
that method is not correct in the case of batteries in which 
the electro-negative plate is carbon, or any other element 
which assumes a different degree of polarity according to the 
altered resistance in the circuit in each case. 

Let g be the resistance of each coil of the galvanometer. 
s be the resistance of the shunt. 
x be the resistance of the battery. 
w be the resistance unplugged. 
e be the electromotive force when the current passes 

through one coil. 
e-i be the electro-motive force when the current passes 

through two coils. 
c be the current in the first case. 
Ci be the current in the second case. 
By Ohm's law we have 

(1) and 



x + 9' s 



g + s 

ci = ^ (2) 

x + 2 -111- + w 
9 + s 

But Ci only equals 77 as it passes through twice as many 



coils to produce the same deflection. 

e 2 e 1 



(3) 



x + -lil- x + 2 g ' s +w 

g+s g + s T 

Now if e = e 1 as is the case in the Daniell battery or others 

in which the electro-negative plate does not polarize 

rapidly, from equation (3) we get 

2 x + 2 . g ' s =%+2 J^l- + w . • . x = w (4) 
g+s ^ g+s 

But if e were not equal to e 1? as would be the case when 
the electro-negative plate was carbon, equation (4) would 
not hold good. 

In such cases the currents would have to be measured by 
the swing of a needle or the fusion of platinum wire for the 
establishment of equations (1) and (2.) 

The outer-protecting covering of the form of electric contact of gai- 

, , n ,. t . . . , (1 vanized protecting 

cable used tor subinarme-mining purposes, being partly wires. 
17 



258 

formed of galvanized iron wires, any accidental contact of 
these, introduced into the system, would produce a copper- 
zinc sea-cell, and give a deflection similar in character to 
that produced by the zinc plate in a wet charge. This 
might be obviated by substituting a carbon plate, within 
the charge at (a,) Fig. 106, for the zinc, and putting a zinc 
one at (6.) The plan hitherto adopted in the experiments 
conducted at Chatham has been to place the carbon f>late 
outside, because it is not liable to be decomposed, by the 
passage of a continuous current of electricity through it, 
when immersed in sea water. 
ca7 a tS?s° f de le ends ^ electrical tests, made at any period after the submer- 
ou comparison. s j ou f a charge, are simply comparisons with the elec- 
trical conditions necessary to practical working perfection, 
which, to insure success, must have existed when it was first 
placed in position. Any deviation from these conditions 
would indicate faults in the system, and would be demon- 
strated by the difference between the results of the tests 
obtained, as compared with those which ought to exist in a 
perfect combination. It is very essential, therefore, that a 
strict record should be kept of all tests applied to each mine 
and cable, with the results obtained. 
Testingarrange- Different testing arrangements must be adopted according 

ments for platinum ° ° 

and tension fuse to the system on which the mines are to be fired. If a 

differ. \ 

platinum wire fuse and circuit-breaker be employed, as in 
Fig. 88, page 215, a large number of Daniell's cells may be 
employed without danger, and every part of the system 
may be tested directly, induing the fuse and circuit breaker 
beyond it. If a high-tension fuse and circuit-closer, ar- 
ranged as in Fig. 89, page 215, be employed, a small num- 
ber of Daniell's or some similar cells must be used with a 
very sensitive galvanometer. The system may be tested 
through the fuse on the direct circuit and to earth, but the 
continuity of the electrical connection to the circuit-closer, 
on the branch, can only be ascertained by actually sending 
a boat out and closing the circuit by running against it. 
loo'.iesi V iov ] % s Should an injury to the insulation of the electric cable 5< 
covery of position e ither between the fuse and the shore, or beyond and be- 

of fault. 7 

tween it and the circuit-closer, be indicated by means of 
the sea-cell test, when the platinum wire fuse and circuit- 
breaker is used, its position may be discovered in the man- 
ner shown in Fig. 107. The positive pole of the battery 
(c z) being put to earth at (c,) the negative pole should be 
attached to a differential galvanometer, one terminal of 
which should be connected to the defective cable (I,) while the 
other should be connected with one terminal of a. set of 



259 

resistance coils (>*.) A well insulated cable (V) of known 
electrical resistance should be attached to the other termi- 
nal of the resistance coils (r,) and should be paid out to 



&g. 107. 



EHiJiIiMiI 




I 

reach the circuit-breaker attached to the defective line. 
The electric cable attached to the circuit-breaker should be 
disconnected therefrom, and attached by a temporary insu- 
lated joint or Mathieson's connector with the line (V.) Sup- 
pose the defect in the line to exist at the point (/,) it is easily 
seen, on reference to the diagram, that the current from the 
battery would divide itself between the two circuits open to 
it, returning through the leak at (/) to the earth-plate (e,) 
and if the resistance in these two circuits were equal, the 
needle would stand at zero,, and this equality would be es- 
tablished by unplugging the coils (r.) 

Let # = the distance, in terms of electrical resistance, of 
the fault from the galvanometer (#,) y=the distance from 
the fault to the circuit-breaker, L=the total resistance of 
the circuit (Z,) including fuse and electric cable up to and 
connecting the circuit-breaker, (this should be ascertained 
by previous tests when the cable and connections were in 
good working order,) L x =the resistance of the line (I',) and 
B=the unplugged resistance in the coils when the galvan- 
ometer needle stands at zero. In this way we obtain two 
equations, viz : 

a?.+#==L 
and ^ = R+ L1+2/ 
from which the values of x and ?/, in terms of electrical resist- 
ance, which would be readily convertible into length, would 
be easily determined. Should the fault exist near the home- 
end of the line, it would be neeessary to place the resistance, 
coils in connection with the same coil of the galvanometer 
as the defective line, in order to make the two circuits bal- 
ance, the resistance of x being necessarily small under such 
circumstances. In this combination it will be observed that 
the electrical resistance of the defect is equally divided 
between the two circuits, and its effect does not in any way 



260 

disturb the conditions necessary to the truth of the equa- 
tions employed. 
a large number j± large number of Daniell's cells may be used in making 

of Darnell's cells ft • , S 

may be used with this test with the platinum wire fuse, without any chance of 

platinum fuse. - 1 " 

an accident. In working a circuit-breaking system in con- 
nection with a platinum wire fuse, it would be convenient 
to keep an electric cable, from the electrical room in the 
fort to the vicinity of the mines, permanently in position, 
for the tests described. This line would also serve for tele- 
graphic communication, which would in the majority of 
cases be required under any circumstances. 
Earth connec- j n order to render this system for the discovery of the 

tion in top of cir- <* ° 

cuit-breaker for position of a fault effective, some means must be adopted 

convenience of ^ . L 

testing. by which a connection with the electric cable in the vicin- 

ity of a circuit-breaker may be rapidly made. The circuit- 
breakers of a system would generally be very close to the 
surface at low water, and a little extra length of electric 
cable, sufficient to enable its extremity to be brought well 
above the surface, with a joint capable of being readily 
opened — one of Mathieson's connectors, for example — would, 
answer every purpose. This and other testing arrange- 
ments might be much facilitated by arranging the connection 
with the earth-plate in the top of the wooden jacket of the 
circuit-breaker. Experiments should be made to test this 
system, and to bring it into a good practical working form. 
Biavier's form- When no return wire, as (I',) Fig. 107, is used, the position 

ula for discovery 7 \ 7/ o 7 i l 

of extent and posi- and extent of a fault may be determined by means of Biavier's 

tion of a fault. ., *n it 

formula, as follows : Let (a &,) Fig. 108, represent the line, 
(a) being the home and (b) the distant extremity, and sup- 
pose a fault of unknown electrical resistance to exist at (c.) 
Let x = the resistance of the portion (a c) from the home 

Fig. 108. 
.g & C y b 



end to the fault ; let y = the resistance of the portion (c b) 
from the fault to the earth connection of the circuit-breaker ; 
and let z =the electrical resistance of the fault itself. Let 
R = the resistance of the line and fuse when in good working 
order, derived from previous experiment ; let S = the resist- 
ance of the faulty line when to earth at (&;) and let T = 






261 

the resistance of the faulty line when insulated at (b.) From 
these we derive the following* equations : 

x + y = R (i) 

x + z = T (2) 

x + 1^ = S (3) 

y + « 

From (l)y = R — a (4) 

(2)s = T — a? (5) 

Substituting these values in equation (3) we have 
« + (B-«)-X(T-») =B 6) 

T R — ^+T — x v ; 

Multiplying both sides by the denominator, we get 
(R + T)x — 2 x 2 + R . T — (R + T ) x + x 2 = (R + T) S — 
2x.& (7) 

From which we obtain 

R.T — ^ = (R+T).S — 2jj.S (8) 

and x 2 — 2 S..T + K.S + T.S — R.T = (9) 

: • x = S i V S 2 + T.R — T.S — R.S (10) 

or j? = S ± V (R— S) x (T — S) (11) 

Substituting this value of x in equation (3) we have 
Z = T — S±. V(R — S) X (T — S) (12) 

From these equations the values of x, y, and s, in terms of 
electrical resistance, are readily obtainable, and the posi- 
tion of the fault may be discovered by converting the values 
of x and y into length. 

If the value of x has been previously obtained, by means 
of Yarley's loop-test, that of z is readily obtainable from 
equation (2.) 

In making tests of this nature much dexterity and previous 
practice is required, as well as considerable electrical skill. 
The difficulty of the problem arises from several causes, 
described by Mr. Culley as follows : 

a l. As the metallic conductor is exposed it forms gal- cable current. 
vanic elements or batteries with, the iron sheath and salt 
water, so that a positive current flows from the cable, through 
the testing galvanometer, to earth ; this is steady and con- 
stant if the cable is not disturbed. 

"2. We have to deal with two unknown resistances: 
that of the wire itself and that between the exposed part 
and the earth ; the first is constant, the second very variable, 
because — 

V 3. The action of the current alters the resistance at the 
point at which the metal touches the water, by coating it 
with substances which differ in conductibility ; and, at the 
same time, the apparent resistance is still further altered 
by the currents of polarization set up by these substances. 



262 

"The action which takes place can be shown by placing 
a piece of cable in a glass filled with salt water and applying 
a current from 40 or 50 cells, one pole of the battery being 
connected to the iron sheath, the other to the copper 
conducting wire. The portion of the cable connected to the 
zinc gives off a stream of hydrogen, while the other becomes 
coated with a chloride of the metal. Thus, if the negative 
pole is connected to the conductor and the positive to the 
sheath, chloride of iron is formed ; and if the connections are 
reversed, chloride of copper is produced. 

" Let us now connect a galvanometer to the cable in such 
a manner that the current from the cable-battery of copper 
and iron in salt water, called the 'cable-current,' shall 
deflect the needle to the right ; the -iron element being, of 
course, always on the earth. 

"If a negative current is now sent into the cable, its 
direction coincides with that of the cable-current, and does 
not affect the direction of the deflection. 

" But the superior force of the testing-battery overcomes 
the cable-current and polarizes its elements. The copper wire 
becomes coated with hydrogen, the iron sheath with chlo- 
ride of iron, so that when the testing-battery current is cut 
off and the cable-battery is again free to act, its action is 
reversed, and the needle moves to the left, under the influ- 
ence of the current of polarization. 

"But the hydrogen gradually enters into combination 
and disappears from the wire, the polarization ceases, the 
needle returns toward zero, passes it, and finally takes up 
its former position to the right, under the influence of the 
cable-battery in its normal state. 

" On the other hand, if we test with copper instead of 
zinc, the needle is deflected to the left, the cable- battery 
again acts as a decomposition cell, but the polarization is 
now in an opposite direction, the copper being coated with 
its chloride, and the iron with hydrogen. When the testing 
current ceases, the needle therefore moves to the right, and 
continues permanently deflected in that direction, because 
the normal current from the cable- battery is now in the 
same direction as the current of polarization. 
condition of a jf we apply a succession of short zinc currents after the 

cable best suited L L J 

for resistance-test, w i re has been coated with the chloride, the needle will still 
take up a right-hand deflection after the battery contact 
has been broken ; but the deflection will decrease after each 
test, and will finally be reversed. The deflection to the right 
is due to the polarization set up by the chloride of copper ; 
each application of the zinc current reduces a portion of 



263 

this chloride, and assists also in removing it mechanically 
by the action of the hydrogen, until after a time the chloride 
disappears and is replaced by hydrogen. The sign of the 
polarization is then changed and the direction of the needle 
is changed also. But there is a moment when the opposite 
actions of the hydrogen and chloride are apparently bal- 
anced, so that the cable battery is inert and the end of the 
wire unpolarized and probably uncoated. Then, and then 
only, can its correct resistance be determined. The object 
of the special method of test is to produce this condition. 

"The test for distance is best made with a differential inf^LoeSli. 
galvanometer. First ascertain the approximate resistance 
in the ordinary way, and clean the exposed wire from the 
dirt and the salts with which it will be coated, by applying 
a zinc current for several hours, occasionally reversing it to 
get rid of any deposit of soda which may occur. The sur- 
face will be roughened by the redeposit of the copper which 
has been dissolved, and will therefore more readily throw 
off the hydrogen evolved by the zinc current. Next apply 
a positive current for the purpose of coating the wire with 
chloride of copper, and finally test with the negative cur- 
rent. The action of the current set up by the chloride of 
copper will make the resistance appear less than it really 
is; but as the chloride is gradually reduced by the testing 
current, in the manner which has just been explained, the 
resistance will appear to increase, moment by moment, and 
the resistance-coils must be lengthened, unit by unit, to 
balance the resistance of the cable, so as to keep the needle 
at zero, until it passes over to the opposite side suddenly, 
under the influence of the change of polarization, caused by 
the copious evolution of hydrogen which will follow. The 
increase of apparent resistance, and the consequent move- 
ment of the needle, is slow and gradual so long as the hy- 
drogen is employed in reducing the chloride, but after the 
reduction is complete and the chloride has disappeared, the 
increase in resistance is enormous and almost instantaneous. 
Unless, therefore, the resistance of the cable has been care- 
fully balanced, so as to follow the variation of the current 
throughout, the test will not succeed, because the neutral 
condition lasts too short a time to permit the adjustment 
of the resistance-coils. 

" In any case a certain dexterity is required, which can Much dexterity 

-iii" --it • -1% ii j> required iu mak- 

only be obtained b}~ practice; but fortunately the practice in g resistaucetest. 
may be had conveniently upon an artificial fault, or a piece 
of insulated wire in a tin can filled with salt water and 
connected to a set of resistance-coils. Induction does not 



264 

affect the test, and as in any ordinary cable the insulation 
is practically perfect, its resistance can be represented as 
accurately by a rheostat as by an actual cable. The higher 
the tension of the battery the less does the opposing current 
of polarization affect the result, for its force seldom exceeds 
two or three cells. The measurement is therefore made 
with a battery of as high a tension as can be conveniently 
procured, 60 cells or more. 
faiufdlpendf on " Tne behavior of a fault varies with the length of wire 
p n sf d! ° f whe ex " ex POsed ; a short fault polarizes and depolarizes very rap- 
idly $ its changes in resistance are correspondingly rapid, 
and its resistance great. If the exposed wire is long, the 
changes are slower and more readily observed ; the resistance 
of the fault is also less. 

" After having well studied the changes of the fault itself, 
make an artificial fault by placing a piece of the cable core 
in a tin can filled with salt water, and alter the length of 
the exposed wire until it behaves in the same manner as 
the cable, and then find its resistance, which will be very 
nearly the same as that of the real fault; so that the distance 
of the break will be the tested resistance of the cable less 
that of the artificial fault. 

"It is a convenient plan to form a table of the resistance 
of exposed wire of various lengths with 6 and 60 cells, 
adding resistances by a rheostat, using the negative current 
and allowing the exposed wire to take up its maximum re- 
sistance. The tests with the 6 cells will be always higher 
than those with 60, that is to say, the resistance of the fault 
will always appear higher when tested with the lower power, 
and the difference between the apparent and real resistance 
will also increase gradually, as the length of the cable itself, 
or the resistance added by a rheostat, increases ; the length 
of exposed wire being constant. 

" Jf a cable is found to give, with 6 and 60 cells, two 
results corresponding to some two in the table, it is probable 
that the length and resistance of the exposed wire is the 
same as that of the artificial fault used in the formation of 
the table, and therefore that the resistance between the testing 
station and the fault is equal to the resistance added to the 
artificial fault. 
Personal equa- " So much, however, depends upon the manner in which 

t ion of observer. ' ' 

the tests for the table were taken, or Upon what we may 
call the 'personal equation 7 of the observer, that every one 
should form a table for himself. The cable must be treated 
in precisely the same manner as the artificial fault, and 
therefore no table will be perfectly correct unless it is made 



•e motion oc- 
curs. 



Tests of combi- 
ation when a 



265 

just before the cable is tested, in order that the precise 
manipulation may not be forgotten." 

The above remarks are made with reference to the tests 
of submarine cables of considerable length, and though 
there is not so much difficulty in testing the short lines 
used for submarine mines, still the same conditions exist 
and must be guarded against and taken into consideration 
on all occasions. Unless this is done, anomalous results, 
caused by the disturbing influences above mentioned, will 
be obtained, and it is necessary to guard against their ac- 
ceptance as due to defects of insulation alone. 

Injury to the insulation of the electric cable necessarily . insulation in- 

° " " jured at points 

occurs at those points where it is subjected to friction, andwne 
in practice the points where it is attached to the sinker or 
mooring apparatus, where it enters the case and where it 
joins the circuit- closer, are those where injury has been most 
frequently found. This is due to the slight motion produced 
by the action of the water, and special precautious must be 
adopted to protect the cable at such points. 

The high electrical resistance of the tension fuse, com- 
bined with the necessity for using a very small battery-cur- Mgi-tension fuse 
rent in connection with it for testing purposes, renders it 
necessary to adopt a totally different arrangement for testing 
when a tension fuse and circuit- closing system is adopted. 
If used with the circuit-closer on a branch, as in Fig. 89, 
p. 215, any test current employed would show a certain 
permanent definite deflection on the galvanometer, due to 
the passage of such current through the fuse itself. Any 
increase in this deflection would indicate a fault in the in- 
sulation of the electric cable, and the extent of such fault 
would be roughly determined by the amount of deflection 
of the needle. Its position could not be determined in the 
manner described for the circuit-breaking system, even with 
very delicate instruments, because the nature of the fuse 
precludes the use of any considerable battery power for 
testing purposes, and there is a permanent passage for the 
current to earth, through the fuse, at a point considerably 
below the surface of the water, where it would be impossible 
temporarily to insulate for testing purposes without bring- 
ing the entire charge to the surface, a proceeding entailing 
much trouble, and to avoid which is one of the principal 
objects of test of this nature. 

A want of conductivity iu the conductor of the electric 
cable would be indicated by a cessation or considerable 
diminution of deflection in the galvanometer. To test the 
conductivity of the portion of the electric cable between 



266 

the charge and circuit-closer on a branch, as in Fig. 89, it 
would be necessary to send a boat out and close the circuit 
by running against it. 

If a circuit- closer were employed beyond the fuse, a defect 
in the electric cable would be indicated by a deflection of 
greater or less amount on the galvanometer. If a fuse of 
high electrical resistance were employed in such a combi- 
nation, it would be extremely difficult to detect a defect in 
the insulation of the cable beyond it. A want of conduc- 
tivity in such a combination would not be indicated on the 
galvanometer on the application of a testing-battery current, 
and the efficiency of the system, in this respect, could only 
be determined by sending out a boat to strike the circuit- 
closer, on which, if the conductivity were good, the galva- 
nometer needle would be deflected. 
Mode of deter- One mode by which the extent of a defect in an electric 
fault, employed cable may be roughly determined is given by Lieutenant 
FLher, R?Nf nan (now Commander) Fisher, E. N., in his work entitled " A 
Short Treatise on Electricity," as follows : 

" Depolarize the main and earth wires by connecting 
them, thus neutralizing the free electricity. After some 
minutes, test the depolarization by again making contact 
between earth, galvanometer, and main wire 5 if no move- 
ment of the needle takes place, the neutralization is com- 
plete. Attach earth wire to test-battery, and with the other 
pole of test-battery make contact with main wire (counting 
'one') and then immediately remove it. Now the earth 
and main wires are slightly polarized, so see if the 'return 
current 7 can be obtained by attaching them to the galva- 
nometer. If the needle moves now, it indicates a large fault ; 
for the wires were not connected with the test-battery for 
much more than a second. If the needle does not deflect, 
repeat the operation 5 leaving the wires this time a little 
longer in the closed circuit, and so on until the return cur- 
rent is obtained. 

" It will be obvious, from what has been said, that the 
longer the test-battery is in the circuit before the i return 
current' is obtained, the smaller will be the fault." 

The current called the " return current," obtained in this 
case, is due to the polarization of the exposed metallic con- 
ductor of the electric cable ; and when a minutely small 
surface of metal is thus exposed, the momentary circulation 
of the current does not produce sufficient polarity to estab- 
lish such a current as would deflect the needle of the galva- 
nometer. 



267 

It must be borne in mind that, with the platinum- wire ^^tJ? 2: 
fuse, a very considerable defect in the insulation of the cable, ™y s fatal when a 

" J platmum-wire fuse 

between the fuse and the firing-battery, (as much as 24 is used, with a 

« / \ tension-fuse it is 

inches of bare conductor, see page 88,) does not prevent the always a serious 

. . „ -,-,.. -.T consideration. 

charge being fired by the application of additional battery 
cells; while a very small defect (^ of an inch for example) 
in the same position would be fatal to the tension-fuse, 
which could not be fired under such circumstances without 
a very large increase of battery power. The discovery of 
the extent of a defect in the insulation is a matter of con- 
siderable importance at all times, but especially when a 
tension-fuse is employed. A small defect in insulation 
beyond the fuse would not be of much importance if a plati- 
num-wire fuse were used, but with a tension-fuse a minute 
defect in such a position would make a sufficient earth con- 
nection to fire the fuse, if the firing-battery were put in 
circuit. With a platinum-wire fuse and circuit-breaking 
system, a very large defect in the insulation of the electric 
cable would probably stop the power of signaling by means 
of the shutter apparatus, but would not prevent the charge 
being fired. With a tension-fuse anil circuit-closing system, 
a very small defect in the insulation of the cable would not 
only prevent signaling by means of the shutter apparatus, 
but, if it existed between the firing-battery and fuse, would 
inevitably prevent the firing of the charge. Taking into 
consideration the relative practical working of the two sys- 
tems,our present experience seems to indicate that a platinum- 
wire fuse, in combination with a circuit-breaking system, is 
most easily tested, and less liable to be rendered practically 
ineffective, than the tension-fuse combined with a circuit- 
closer. With the latter, too, the sea- cell is not so applica- 
ble for testing purposes, in consequence of the high electrical 
resistance of the fuse. 

When a defect has been found to exist in any part of the . A defective 

^ x charge or cable 

system, it should be taken up and repaired with the least ? h £ uld be at once 
possible delay, unless the presence of an enemy or some 
other imperative cause interfered to prevent it. With this 
object in view, arrangements are made to admit of raising 
the charge and circuit-closer (or circuit-breaker, as the case 
may be) with facility. Should a defect exist in the electric 
cable it should be under-run, and if it be a defect in insula- 
tion, its position may be discovered by keeping a test battery 
in connection with it during this process, and the moment 
the defect was lifted out of the water, its position would be 
indicated by a sudden reduction in the deflection of the gal- 
vanometer needle, as described in the tests of electric cables, 
page 246. 



268 
Electrical in- The instruments adapted for testing purposes are the 

struments used m L & i i 

testing. reflecting electrometer, the reflecting, astatic, detector, and 

differential galvanometers, Wheatstope's bridge, resistance 
coils to 10,000 B. A. units, (or ohms,)" the thermo-galvanome- 
ter, rheostat, and a few battery-cells of size adapted to the 
tests to be applied. 

tromSer ting elec " ^ ne ren " ec tiug electrometer is a very delicate instrument, 
requires very careful handling, and can only be used by a 
practiced electrician. Its use must therefore be restricted 
to important stations and special tests of a delicate nature. 
Reflecting gai- The reflecting galvanometer is also a very delicate instru- 
ment, adapted for fine tests of a delicate character ; it suse 
may therefore also be restricted to important stations where 
delicate tests are required. 
Astatic gaivan- The astatic galvanometer, though less delicate than the 

ometer. ° ' 

reflecting instrument, is very sensitive and is applicable to 
very fine and delicate tests. It may be made in a very com- 
pact and portable form, and should be supplied to all sta- 
tions where submarine mines are used for defensive purposes. 

Detector gai- The detector galvanometer is generally made with a ver- 
tical needle, and is used for all the rougher tests requisite 
for submarine mines. For this purpose it should be made 
as sensitive as possible, commensurate with small size and 
portable form. An insensitive detector galvanometer is 
of no use for the tests employed in connection with submarine 
mines. These instruments should be supplied to all stations. 

Differential gai- The differential galvanometer is an extremely useful in- 

vano meter. ° 

strument for electrical purposes. The results obtained with 
it are very accurate, generally sufficiently so for all purposes 
connected with submarine mining operations. Two instru- 
ments of this nature have recently been devised, viz, Lati- 
mer Clark's, double shunt differential galvanometer, and 
the post-office pattern differential galvanometer, the latter 
designed by Mr. Becker, electrician to Messrs. Elliott 
Brothers. A diagram of the connections of Latimer Clark's 
instrument is given in Fig. 104, page 252. It is extremely 
portable and capable of being used in a great variety of 
combinations as described in Mr. Latimer Clark's very 
excellent hand-book on electrical measurements. The post- 
office pattern instrument is very similar in principle to Lat- 
imer Clark's. It differs in having only one shunt, and in 
being constructed with a suspended needle, instead of one 
working on a pivot. It is a more delicate instrument than 
the former, only inasmuch as the principle of suspension 
is a more delicate combination than that of a pivot, other 
details of construction being similar. It is not so portable 



269 

instrument, and cannot be used in a 
boat, or in any position where there is no steady foundation 
to put it on. A good differential galvanometer should be 
supplied to all where" submarine mines are employed for 
defensive purposes. 

The well-known application of the division of electrical bv ^oreiec"i e C ai 
currents for testing purposes, devised by Professor !Sir balance - 
Charles Wheatstone, and called " Wheatstone's bridge," is 
an extremely delicate apparatus for the measurement of , 
electrial resistance in all cases into which the balancing pro- 
cess enters. In combination' with the reflecting galvanom- 
eter, it is extensively used on all submarine lines of electric 
telegraph. The information afforded is similar in character, 
though more minutely accurate than that obtained with the 
differential galvanometer. Its employment may therefore 
be restricted to the more important stations and more deli- 
cate tests required for submarine mining purposes. 

Eesistauce-coils, capable of measuring up to 10,000 ohms, Resistance-coiie. 
(B. A. units of electrical resistance,) should be supplied to 
all stations in which submarine mines form apart of the 
defense. Resistance-coils are necessary in most of the tests 
described, either in combination with the differential galva- 
nometer or with Wheatstone's bridge and the reflecting 
galvanometer. They are made in two forms by Messrs. 
Elliott Brothers, either combined with Wheatstone's bridge, 
or in a smaller and more compact form, consisting of the 
resistance-coils alone without the bridge. 

The use and construction of the thermo- galvanometer, as Thermo-gaiva- 

> nometer. 

designed by Colonel E. W. Ward, R. E., is given in ±lie 
Course of Instruction in Military Engineering, page 140, para- 
graph 302. This instrument should be supplied to all sta- 
tions where the platinum wire fuse is used as the electrical 
igniting agent. 

An ordinary rheostat is an extremely convenient instru- Rheostat. 
ment for use with the thermo-galvauometer, and should be 
supplied with it to all stations. 

Testing-batteries generally consist of a few Darnell's or . Testing-batter- 
other similar cells, of small surface, and should be made in 
a portable form arranged in a wooden case. The nature of 
testing-batteries must be adapted to the nature of the tests 
to be applied. Where Abel's fuses are used, a current of 
small quantity and low electro-motive force must be applied, 
and Mr. Abel has designed a very compact form of sand 
battery with this object in -view. In ttiis battery, one or 
more cells may be rapidly introduced into the circuit, by 
the insertion of a contact-plug provided for the purpose. 



les. 



270 

Three or four testing-batteries, suited to the nature of the 
combination employed should form a portion of the equip- 
ment of every station where submarine mines are used. 
cons of instru- In all cases, the coils of the instrument and apparatus 
tus must kSS must be suited to the nature of the battery power used for 
testing "currents testing and w r orkiug purposes. Where a tension fuse is 
appied. employed, fine coils, composed of a considerable length of 

insulated wire, are essential, so that the comparatively small 
currents, necessarily employed in testing, may produce a 
sufficient deflection of the galvanometer needle. On the 
other hand, when a platinum wire fuse and quantity-battery 
is used, coils composed of large and thick wires must be 
employed, because the current of a quantity-battery would 
destroy the coils of any instrument composed of fine wire, 
if passed through it for an instant. 
Qualification of The officers, non-commissioned officers, and men employed 

officers and men . ,. . n , . ,i,t 

employed. m working any system of submarine mines must be thor- 

oughly instructed in electricity, and further be well up in 
telegraphy, visual signaling, and in the use and manage- 
ment of boats and mooring apparatus. It has been found 
that the course of instruction necessary to qualify thoroughly 
consuuuion of & de ^ or tn * s sery i ce occupies a period of about six mouths. A 
tachment, detachment for work with a system of submarine mines 

should consist of one officer and twenty thoroughly instructed 
non-commissioned officers and men. This may be con- 
sidered as the unit, and one or more such detachments 
would be required according to the extent of the work to 
be performed. Five such detachments would form a com- 
pany. 



CHAPTER XIV. 

CLEARING CHANNELS OF SUBMARINE MINES. 

The best method of clearing a channel defended by sub- 
marine mines, though more a naval than a military question, 
is one concerning which a certain amount of knowledge is 
requisite for all engaged in the use of machines of this 
nature. 

Passive obstructions, in the shape of booms, nets, &c, use of passive 

., _ -,,-,1 i , • obstructions com- 

would generally be used to check an enemy's operations bined with sub- 
against the mines, and to impede boats and small vessels i u mannemi1 
their approach toward them. In their project for the de- 
fense of Venice, in 1866, the Austriaus proposed to place a 
light boom in advance of their outer group of mines with 
this object in view. 

The hostile removal of submarine mines implies the ab- d^Sne^by^Imau 
sence of guard-boats and of land defenses, or the inability of f^/""^^ by 
the latter to see the operation owing to the darkness or fog. 
Where electrical igniting apparatus is suspected, the banks 
of the river or roadstead would, if possible, be searched with 
a view to intercept the wires. The advanced booms and 
nets, if any, would be blown up, or, if secrecy be an object, 
cut, or turned by boats rowing round their shore ends. 
Lines of boats would then advance in couples, towing small 
hawsers between them weighted about the center, with a 
view to sweep the suspected waters for buoyant mines and 
circuit-closers, their own light draught giving them sufficient 
immunity. When a submarine mine or circuit-closer was 
thus caught, a signal would be made to other boats to 
avoid the locality, while the. two boats concerned, crossing 
the ends of their hawser, would cautiously pull the mine up 
to the end of a long outrigger, (or davit,) and, carefully 
cutting the mooring rope, tow the mine into shallow water. 
Other lines of boats might follow, dragging small grapnels, 
in the hope of intercepting the wires of such ground mines 
as were unprovided with circuit-closers. The channel being 
thus partially cleared, small steam-vessels might advance 
in pairs, dragging between them large hawsers, weighted 
with chains and armed with grapnels; while pushing some 
sixty feet before each vessel a submerged framework, armed 
with hooks and nets, extending below the keel and beyond 
the broadsides, which might intercept and explode harm- 
lessly the usual mechanical submarine mines. Even with 
very slow speed and every precaution great danger would 
be incurred for steam-vessels in the case of circuit-closers 



272 

attached to ground mines, as the former might be dragged 
forward by the projecting frame and close the circuit when 
its mine was actually under the bottom of the ship. The 
breadth of channel so cleared should be carefully marked to 
prevent advancing vessels passing over unsearched ground. 
It is obvious that such operations could only be undertaken 
in undefended and unguarded w r aters. And it is worthy of 
remark that most of the United States vessels destroyed by 
submarine mines were lost while advancing in waters pre- 
viously dragged or otherwise examined by boats. The 
introduction of electrical apparatus increases the difficulty 
of clearing channels, and too much precaution cannot be 
observed in navigating waters which are supposed to have 
been defended by submarine mines, even after they have been 
most carefully searched. If advanced booms or nets are not 
used by the defense, barges or rafts, with submerged frames 
to give deep draught, might be employed to drift over the sus- 
pected waters, with a view of exploding the mines by con- 
tact, should the conformation of the river or roadstead 
admit of it. If the tidal stream be very strong, light grap- 
nels might be dragged over the bottom by these drifters, 
with a view of fouling the electrical cables or mooring ropes 
should the nature of the ground favor the proceeding. It 
is evident that a rough or rocky bottom, or the employment, 
by the defense, of a heavy chain laid across the channel in 
advance of the mines on hard ground might convert the 
grapnels into anchors, and thus defeat the primary object 
of exploding self acting mechanical mines by contact. In 
many places, in the Med way for example, a heavy chain 
would soon sink into the mud, and become as far covered 
as to offer a small chance for catching the grapnel: under 
the same conditions, however, the electric cables would 
equally sink into the bottom and be less likely to-be fouled, 
projectingframes Iii their operations against the confederates, the Federal 

or nets carried in _ n . ., , , 

advance of a ves- fleets m many cases used projecting frames and nets, in 
front of the bows of the leading vessels, in which the sub- 
marine mines, arranged for mechanical ignition, were in- 
tended to be caught without danger to the ships. Notwith- 
standing this precaution several vessels were sunk and 
damaged. In many cases the charges were not fired at all, 
but this was due more to the failure of the igniting apparatus 
than to any special value attaching to the mode in which 
the machines themselves were caught : with the more effi- 
cient means we now possess for finding mechanical mines, 
combined with the vastly increased size of the charges pro- 
posed to be employed, it is probable that this mode of clear- 
ing a channel would be a far more dangerous and difficult 



273 

operation; the mines would be fired with far greater cer- 
tainty, and their radius of destructive effect would be so 
much increased as to necessitate a frame, extending to a 
much greater distance in front of a vessel than those used 
iu the operations alluded to. 

In the case of mines fired by electrical agency, the danger 
to a vessel using a projecting fender would be still greater 
if circuit-closers, in connection with ground mines, were 
to be attacked. In such a case the circuit-closer only would 
be caught by the fender, and the vessel would be more or 
less over the actual mine, when the collision, with its con- 
sequent explosion, would take place. 

Fenders of this nature should, in all cases, be constructed 
to extend to as great a depth as possible below the water 
level, so as to catch mines and circuit-closers not only near 
the surface but to a considerable depth below it. 

The course adopted by the Federal fleet, in searching 
channels for submarine mines, was first to send forward 
boats to drag for them and to follow the boats up with ves- 
sels fitted with fenders of the nature described. This system 
seems to be that best calculated to insure success. 

The following mode of operation, which may or may not Suggestion for 

rt L ' J •' the use of tram 

be capable of practical employment, is suggested for the mortars, fired a- 

^ r i J ? »o multaneously, in 

consideration of naval and artillery authorities. It consists searching for 

mines. 

in simultaneously firing a couple of mortars, pointed in such 
a manner as to cause their shells to diverge from each other, 
by electricity, using very small charges of powder, only just 
sufficient to give a range of 400 or 500 feet ; and having pre- 
viously attached a chain to each of the shells, and another con- 
necting the two shells together, the effect would be to cast the 
chains out and inclose a certain area. By hauling on the 
two extremities of these chains, any mine within that 
area would be caught and probably injured or destroyed. 
In certain parts of the world, at Bermuda for example, the 
sea water is so extremely clear that, in fine weather, such 
an object as a submarine mine would be easily distinguish- 
able from a vessel's tops at a considerable distance and at 
a great depth ; in such a case this mode of clearing a 
channel, by throwing out a chain attached to a couple of 
shells, might be successfully employed. Very clear water 
would be a favorable condition, as regards the search for 
submarine mines, whatever mode of proceeding may be em- 
ployed. 

In this, as in all operations of a similar nature, the same 
difficulties, as regards interruption caused by the fire of 
guns defending the system of mines, would still exist. 
18 



274 

To be effective it is probable that a specially fitted vessel 
and a special crew would be required. Such au operation 
would be comparatively easy if the mortars were fired from 
the shore or from a vessel anchored in a harbor in smooth 
water, but it must be borne in mind that, to be effective, it 
should be capable of being used in moderately rough water 
and from a vessel not necessarily at anchor. 
ne? by ri 8ubm C arine Another method, which has suggested itself in the course 
explosions. of experiments carried on at the school of military engineer- 

ing, Chatham, during the autumn of 1870, is to fire large 
charges of gun-cotton in positions which are supposed to be 
studded with submarine mines, with a view to destroy- 
ing any charges which may be within the radius of explo- 
sive effect; to proceed, in point of fact, on the same princi- 
ples which have been found effectual in attacking a land 
fortress defended by counter-mines. The experiments 
made last autumn demonstrated that a charge of 432 pounds 
of gun-cotton, fired under a head of between 40 and 50 feet 
of water, destroyed and rendered ineffective a series of 
mines placed in its vicinity, to a radial distance of at least 
120 feet from the point of explosion. It would not be diffi- 
cult nor tedious to carry on a series of explosions, of charges 
of 500 pounds of gun-cotton, with a little previous preparation. 
They might be easily maneuvered and fired from an ordinary 
steam-launch,, and two or three of these boats moving 
abreast, firing their charges, and gradually advancing over 
the ground thus made good, would in time clear a channel 
sufficiently wide" to admit of the safe passage of the largest 
iron-clad. During such an operation these boats would, no 
doubt, be fired on by the guns covering the mines, and it 
would be absolutely necessary to cover them to the utmost 
extent, by the guns of the attacking force. The night or 
foggy weather would be the most favorable time for opera- 
tions of this nature. 
a slow speed to in whatever way a boat or vessel may be employed in 

be employed by . 

vessels searching searching for submarine mines, or whatever may be her size, 
it is of the utmost importance that she should move as 
slowly as possible — in fact, with the least possible speed, 
commensurate with efficient steerage-way. In moving it 
at a slow speed she would be less likely to explode a 
charge by contact, and would be more easily checked if 
found to be getting into danger. 

The clearing of a channel defended by submarine mines, 
would, under any circumstances, be a tedious and danger- 
ous operation, and the delay thus incurred could not fail to 
be of immense advantage to the defense, even if every ship 
and boat in the enemy's fleet escaped injury. 




CHAPTER XV. 

LOCOMOTIVE TORPEDOES. 

We now come to the locomotive class of machines for 
producing submarine explosions, adapted for use in offen- 
sive warfare. These are more especially a naval arm, and 
to them the term torpedo is properly applicable. They may 
be divided into three classes : 

1st. Those to which motion is eiven bv a ship or boat to outrigger tor- 

pecloes. 

which they are attached, and from which they may be 
maneuvered. 

2d. Projectile torpedoes,or those possessing iu themselves Projectile torpe- 
the power to move through the water, when once started, in 
any particular direction. 

And 3d. Drifting torpedoes, or those dependent for tbeir d0 ^ iftiI!g torpe " 
motion on the tide or current of a stream. All three classes 
are applicable, generally, for the attack of vessels at anchor 
or in motion, booms or obstructions of any sort, ponton 
bridges, &c. ; some forms may be most effectually used 
against stationary, and others against moving objects to be 
attacked. 

To the first class belong those projected from a boat or 
ship by means of a spar or outrigger, as well as Harvey's 
towing torpedo, and all similar contrivances. 

To the second class belong those propelled by compressed 
air, as Lupin and Whitehead's torpedo; those to which 
motion is given by means of a rocket composition, as sug- 
gested by Mr. Lancaster, the gun-maker, and Mr. Quick, 
engineer, royal navy, and all similarly propelled. 

To the third or drifting class belong McEvoy's torpedo, 
Lewis's torpedo, and those of a similar nature. 

The idea of attacking vessels by means of boats, either 
specially constructed for the purpose, or with the apparatus 
adapted to existing forms, appears to have originated with 
Fulton, in 1803 ; it was, however, considerably developed 
and brought into a practical working form during the civil 
war in America. 

The confederates made and used several special boats, special outrig- 

x ' ger torpedo boats 

some propelled by steam or by a screw propeller, worked employed by the 
by manual labor, to carry a torpedo attached to a spar or 
projection in front, to be exploded in contact, or nearly so, 
with the hull of the vessel to be attacked. The specially 
constructed boats were provided with water-tight com- 



276 

partnients, and when these were filled the whole was so far 
submerged as to show very little above the surface of the 
water. The general results obtained with them were 
unsatisfactory ; they were very dangerous to navigate in a 
sea, and one which had already sunk four times, drowning 
four crews, finally went down with a fifth crew in destroy- 
ing the United States corvette, " Housatonic," oft Charles- 
ton, South Carolina, on the night of the 17th of February, 
1864. The corvette was sunk, but nothing was ever again 
heard of the torpedo-boat. This was the only successful 
attack out of five attempts made by the confederates with 
boats of this nature, and the results were so discouraging 
that they turned their attention to the use of ordinary ship's 
boats for this service. 
pedoesHtted 'To ^ ne results as regards ship's boats carrying torpedoes on 
Srd?nar^c.ons a truc- ou * r ^^ ers or s P ars ? ^° De pushed out and fired in close 
tion - proximity to a vessel's hull, were more satisfactory. Several 

steam-launches were adopted for service in this way by both 
Federals and confederates. Their general arrangements con- 
sisted of one or more long spars, to the extremities of 
each of which a torpedo was attached, carried in such a way 
as to be readily pushed out from the bow of the boat imme- 
diately before the absolute moment of attack, the charge 
being fired by the percussion of a self-actiug mechanical 
fuse on the hull of the enemy's vessel, or by means of an 
arrangement fired by a trigger line ; this latter combination 
was generally employed by the Federals. The confederate 
torpedo-boat "Squib," which attacked and so seriously dam. 
aged the United States frigate u Minnesota,'' lying at anchor 
in Newport News, at 2 a. m. on the morning of the 9th of 
April, 1864, was a steam launch fitted in this way. A very 

Results obtained _ , „., . .. . . • /^ j. • tt j* 

more satisfactory, good account of this operation is given in Captain Harding 
Stewart's Notes on Submarine Mines. The torpedo-boat, with 
which Lieutenant Oushing, of the United States Navy, suc- 
cessfully attacked and destroyed the confederate ram " Albe- 
marle," which was, at the time, alongside the wharf at 
Plymouth, eight miles above the mouth of the Roanoke 
River and carefully protected by a strong timber boom and 
other obstructions, was an ordinary man-of-war's steam- 
launch. A good account of this very daring enterprise, 
which was carried out at 3 a. m. on the 28th of October, 
1864, is given in a book entitled Submarine Warfare, Offensive 
and Defensive, by Commander Barnes, United States Navy, 
page 142. In this latter work, at page 154, there is also a 
very good account of the United States torpedo- vess el 



tious. 



277 
"Spuvfcen Duvvil," of 200 tons, especially designed for use . Spuyten Duy. 

L i ' L " = vil, construction 

with an outrigger torpedo to be pushed out, below her water disapproved by 

00 k L 7 committee on 

Hue, through a water-tight opening in her bow. This vessel f™^ obstruc- 
ts very completely fitted up, but no opportunity has hitherto 
occurred of trying her against an enemy's vessel. The con- 
struction and general arrangements of tbe " Spuyten Duy- 
vil" were condemned by the committee on floating obstruc- 
tions, as may be seen from the following extract from their 
report, page 138 : "In the beginuing of 1865, the plans of 
Mr. Wood's outrigger torpedo apparatus were offered to 
Her Majesty's government, but a careful examination con- 
firmed the opinion originally entertained as to the too com- 
plicated nature of the machinery. The arrangement for 
giving lateral motion to the outrigger is obviously unneces- 
sary, inasmuch as this may be accomplished by the use of 
the helm ; it is also dangerous, because it renders the out- 
rigger liable to get across the stem at high speeds, when the 
spar might snap, the torpedo being thus under the bottom. 
The separation of the torpedo from the outrigger before 
exploding, as proposed, would involve the danger to the 
operating ship of advancing within the sphere of its destruc- 
tive action when the explosion takes place. The committee 
therefore fully concur in the opinion expressed by Rear- 
Admiral A. Cooper Key, 0. B., then captain of Her Majesty's 
ship i Excellent,' that this plan ' is not worth adoption, or 
even of trial with a view to adoption in our Navy.'" In 
addition to this vessel the United States possessed a number 
of steam-launches, each carrying one 12-pounder boat how- 
itzer, and a crew of 15 men, fitted for outrigger torpedo 
service, the torpedoes being carried on spars resting on 
crutches, and ready to be run out and fired at short notice. 
Six low free-board monitors were also similarly fitted. 

No attempt has been made in this country to fit up any 
special vessel, such as the " Spuyten Duyvil," for offensive 
torpedo sef vice, our naval authorities being, it is understood, 
of opinion that such operations as the attack of a vessel by 
a torpedo-boat would be similar in character to the cutting 
out of a ship at anchor in an enemy's harbor, which was so 
successfully performed during the French wars in former 
times; they therefore propose to adopt boats and small 
vessels, of classes already existing in the Royal Navy, for 
this service. The following description, extracted from a book 
entitled " A Short Course of Electricity '," by Lieutenant (now 
Commander) Fisher, R. N., late instructor in electricity and 
torpedoes onboard Her Majesty's ship "Excellent,'' gives 
a good idea of the arrangements proposed as most suitable 
for the purpose required. 



service. 



278 
Fittings of ex- u £ general description will be given of the maimer in 

cellent s steam- o j. r> 

\ & ™?* fortor v edo which a, steam -launch and gig are fitted in Her Majesty's 
ship " Excellent*' for torpedo purposes, as shown in Fig. 
109, both giving most successful results. 

u The fore part of the boat is covered over with a canopy, 
which is spread over a fore-and-aft pole, resting on two 
wooden crutches, and is tightly laced down to a foot-board 
that extends round the fore part of the boat, just inside the 
gunwale, to allow the crew to work outside when required. 
At about two feet abaft tbe stem a projecting cross-piece is 
secured to both gunwales, having at either end an iron 
crutch, in which rests the outer part of the torpedo-pole 
when not in use, and which serves as a fulcrum for the pole 
when rigged out ; a pin across the crutch prevents any 
chance of the pole being lifted out of it. An upright, similar 
to a rocket stanchion, ships into a step on either side of the 
boat, outside of the gunwale, and is secured to it by iron 
clamps; these stanchions, which are about six feet in 
length, have attached to, and projecting from, their exterior 
sides, an iron rod, the torpedo-pole working between the 
iron rod and the stanchion, so that when the heel of tbe 
torpedo-pole is triced up to the head of the stanchion, (thus 
rigging it out and at the same time submerging its outer 
extremity,) the pole is confined between them, and thus any 
lateral movement is prevented. 

u The rigging-out rope of the torpedo-pole is led from the 
stern-sheets through a small block at the head of the stan- 
chion, and made fast to the pole about a foot from the heel. 
A back rope is secured to the heel, for the purpose of easing 
out the pole, and of rigging it in again when required. 
When the poles are rigged in, their heels rest on crutches 
on the outside of the after part of the boat. The height of 
the stanchion, its distance from the fulcrum-crutch, and the 
length of the pole, depend on the depth to which the torpedo 
is required to be submerged and on its charge ; but appended 
are the dimensions of the " Excelleut's "' torpedo-gig and 
fittings, constructed to admit of 50 pounds of gunpowder, 
submerged nine feet, being fired with perfect safety to the 
boat and its crew. Such a charge so placed, we know from 
experiment, would inflict irreparable damage on any ship 
as at present constructed, if exploded in contact with her 
bottom ; and as it is probable that the horizontal section of 
its ellipsoid of destruction at the depth of nine feet would 
not be less than a circle of five feet radius, great mischief 
would doubtless be caused by it even when not exploded in 
perfect contact, but within the assumed live-feet limit. 



or — - 



9/i » 
Jl/t 



ft 5>» *"> 



-#T--A-V' 




279 

"The 'ExcelientV steam-launch, fitted up in a similar 
manner, carried a torpedo charged with 100 pounds of fine- 
grained powder, the only exceptions to the torpedo gig ar- 
rangements being that it was submerged to a depth of 10 
feet, and the torpedo when in position was 25 feet (instead 
of 17J feet) from the stem, in the direction of the pole. No 
water was shipped on the explosion being effected, nor was 
there the slightest inconvenience of any sort experienced. 
Dimensions of torpedo gig and fittings. 

Length of boat 30 feet. 

Beam 5J feet. 

Length of canopy lOf feet. 

Distance of cross-piece from stem , 2 feet. 

Length of poles 28 feet. 

Thickness of butt-end of poles 4J inches. 

Length of stanchion ...» 6 feet. 

Distance from stanchion to the cross-piece in 

stem 5 feet. 

Distance from after crutch to stanchion 10| feet. 

"Each stanchion is supported by two f-inch iron stays, one 
going to the opposite gunwale and the other supporting it in 
a fore-and-aft direction." 

Rear- Admiral A. Cooper Key, C. B., F. R. S., then di- 
rector general of naval ordnance, remarked upon the above - 
apparatus and experiments : " That it would be rarely advisa- 
ble to risk a boat's crew for the purpose of using a charge of 
40 pounds, which must be placed in actual contact with the 
bottom of the ship it is intended to destroy. The uncer- 
tainty attending such an attempt must lead to failures. I 
consider that 100 pounds of gunpowder, or its equivalent 
in gun-cotton, is the least charge that should be used." 

The use of such service-charges would involve a greater 
strength in the apparatus and longer poles. 

Fig. 109 is copied from the Report of the Committee on Description 
Floating Obstruction-sin the following description as extracted 
from it: (a) shows the canvas covering, (b) the outrigger 
rigged in, (c) a stanchion, (d) the guide rod, (e) the fore-and- 
aft stays of iron, (/) the stays ath wart-ships, (g) the torpedo 
for 10 pounds of gunpowder or 10 pounds of gun-cotton j 
{g 1 ) the torpedo for 100 pounds of gunpowder, and 25 pounds 
of gun-cotton ; the dotted lines show the arrangement of boom 
recommended by the committee on floating obstructions, the 
firm lines the form adapted for a charge of 10 pounds of powder 
only, (h) the foremost crutch, (/&') the pin to retain the out- 
rigger in the crutch, (i) the after crutch, (h) the fore-and- 
aft mooring pole, (?) the securing screw of the stanchion, 
(m) the securing screw of the cross-piece, (n) the step for 



280 

the stanchion, (o) the securing clamp for the stanchion, (p) 
the foot-board, (q) the cross-piece, (r) the topping-lift, (s) 
the inhaul, (t) the outhaul, (it) the conducting wire. 

"Only one outrigger should be placed in position for 
action at a time, otherwise the first explosion might injure 
the other torpedo. 

" It would be necessary to impart increased strength to 
these fittings to enable them to withstand the explosion of 
serviceable charges of 100 pounds and upward of gun- 
powder. In an experiment of this description material 
injury was sustained by the apparatus. 

" The dotted line thus - ■ — represents the com- 
puted area of principal destruction of 100 pounds of gun- 
powder at the depth of greatest effect." 

Outrigger torpedoes are applicable for the attack of booms, 
ponton-bridges, vessels at anchor or moving very slowly, and 
similar objects. 
Harvey's sea Harvey's sea torpedo also belongs to the first class of 
torpedo; descnp- wea p 0ns? being maneuvered from a ship in motion. It is a 
joint invention of Captain John Harvey and Commander 
Frederick Harvey, E. N., and consists of a case (a) of No. 18 
B. W. G. sheet-copper, of the form shown in Fig. 110. This 
case may be made of any size ; the dimensions, as show T n in 
the figure, are those calculated to contain a charge of 76 
pounds of gun-cotton, or an equal bulk of. other explosive. 
This charge would be sufficient to sink any vessel if fired in 
contact with her hull, and is of convenient size to work with 
facility from a ship's deck. The form adopted is similar to 
the machine called an "otter," used by poachers for fishing 
purposes, and its mode of propulsion through the water is 
identical therewith. Outside the sheet-copper, which forms 
the internal water-tight portion of the apparatus, is a thick 
wooden casing strengthened with iron plates, to preserve 
the former from injury. To the bottom of this wooden 
casing is attached a keel of iron, (&,) with a leaden covering 
on the lower side, to keep the apparatus upright while 
floating in the water. The weight of iron used is regulated 
by the speed of the vessel from which the torpedo is to be 
maneuvered, and it should be sufficiently great to sink the 
whole apparatus when complete with charge, &c. This 
capacity to be submerged at wall is essential to the proper 
maneuvering of the apparatus, and, when the towing line 
is cut away, its effect is to sink the whole to the bottom, 
and thus prevent chance of injury to a friendly vessel. Lines 
are arranged, as shown at (c,) to enable the torpedo to be 
towed at an angle diverging about 45° from the direction of 



281 



tbe course of the vessel from which it is worked. The towing 
line is composed of several strands of galvanized steel wires 
over a hemp core, forming a l|-inch wire rope. The towing 
line passes through a ring in connection with the guiding 
ropes (c,) thence through another ring (d) on the stern of 



Fig. 110. 



4 10 





the apparatus, and is connected with a bnoy, arranged to 
prevent the torpedo sinking too deeply for subsequent 
work during any temporary slackening of the towing line. 
A knot on the towing line prevents the buoy being drawn 
too closely up to the torpedo, but being beyond the ring 



Natui 



282 

(#,) directly the towing, line is cut at any point, the latter 
slips through, and the torpedo itself is disengaged and 
sinks. 
ofexpio- The charge of gun-cotton or other explosive is contained 

sive used. <=r o a. 

in two compartments within the sheet-copper case which is 
divided in the middle. A loading hole, 1J inches in diam- 
eter, to be closed by a water-tight screw plug, is provided 
for each compartment. 
Mode ot firing. The charge is arranged to be fired by means of a metal 
bolt (/) in connection with a sulphuric acid fuse. When 
the bolt is forced down it breaks a glass vessel containing 
sulphuric acid, which, falling on a chemical mixture, pro- 
duces heat and fires the priming of the fuse, which in its 
turn ignites the charge. The priming charge is contained 
in a vertical copper cylinder, placed in the center of the 
torpedo, and only divided from the two sections of the charge 
by the thin metal of which the cylinder is composed. The 
fuse piece, with firing-bolts, &c, complete, is carried sepa- 
rate from the charge, and only screwed into it just before 
the torpedo is launched overboard for the attack of a vessel. 
The firing-bolt is provided with a safety-key, passing through 
a hole in the former, and till it is removed the bolt cannot 
be pressed down and the charge cannot be fired ; this key 
is drawn out by means of a line attached to it and veered 
out from the ship simultaneously with the tow-line. The 
firing-bolt may be arranged to explode the fuse on any given 
pressure being applied; for this purpose a pressure of about 
CO pounds has been found to be convenient. The pressure 
required to withdraw the safety-key should be arranged at 
about 30 pounds. Pivoted on the bow of the torpedo are 
two levers (g) and (/«-,) one (g) passing vertically over it 
toward the rear, the other (h) on the side of the apparatus 
which is most likely to come in contact with the vessel to 
be attacked, always on the opposite side to the directing 
lines (c.) The lever (g) is arranged over the head of the fir- 
ing-bolt; on coming in contact with the bilge of a vessel, it 
would be pressed down, carrying with it the lever (i) and the 
firing-bolt, which would break the glass capsule containing 
the sulphuric acid, and thus fire the fuse and consequently 
explode the charge. The lever (h) performs the same office 
when acted on by side pressure against a vessel ; when 
pushed in toward a topedo, it draws in a lanyard iu connec- 
w ith the lever (i) and pulls this latter down, acting on the 
firing-bolt with the same result as before. 
Different forms of Different forms of torpedo are em ployed for each side of the 

torpedo required . 

for each side of vessel, the lever (h) being always so arranged as to be on that 
side of that apparatus which, when floating in the water, is 



283 

away from the ship from which it is maneuvered, the tow- 
lines being on the side nearest to the vessel. 

In order to maneuver torpedoes of this nature, the ship^^eofmaneuv- 
should be provided with a couple of drums, with brakes 
attached, on either quarter. One of these drums carries 
the tow-line, the other the safety-key line, which are veered 
out uniformly together; they should be of such dimensions 
as to hold a length of 210 fathoms of each. To attack a ves- 
sel the proper torpedo is launched overboard by its towing- 
line and gradually veered out to any distance required, 
usually about 150 yards, the vessel being kept in motion 
during the whole process. The brake is then put on, which 
has the effect of bringing the torpedo to the surface and 
carrying it along in a line parallel to the ship's course and 
diverging from her quarter at an angle of 45 degrees, and 
at any distance from 150 yards upward, that may be re- 
quired. A reserve of about 150 yards of line is kept on the 
drum for future use. The torpedo is visible from the deck 
of the vessel using it during the whole of this operation, and 
its approach toward the vessel to be attacked may be readily 
watched. As it approaches its object the safety-key is with- 
drawn by means of the line provided for the purpose, the 
brake is relaxed, and, the pressure on the towing-line being 
thus removed, the torpedo sinks for a moment, the brake is 
again applied just at the time when it is supposed the tor- 
pedo is under the vessel to be attacked, it rises in conse- 
quence of the pressure thus applied to the towing-line, comes 
in contact with the bilge, one or both levers are forced down 
and act on the firing-bolt, and the charge is fired. 

Commander Harvey has applied Captain McEvoy's circuit- Electrical mode 
closer for firing his torpedo by electricity ; he seems, how- 
ever, to prefer mechanical ignition on contact, in consequence 
of the danger of fracture or injury to be apprehended in 
veering out the insulated conducting wire, which must be 
made in the center of the towing-line and consequently be 
subjected to a considerable strain. He is of opinion, more- 
over, tii at electrical ignition would not, under any circum- 
stances, be so certain in its action as mechanical action. 

Experiments with this form of torpedo have been carried Most useful a P - 
on by the government at Portsmouth and Plymouth, and it picaiou " 
was maneuvered with great success. To render it thoroughly 
efficient, however, in rough water and in the open sea, much 
skill and practice are necessary. This apparatus is adapted 
for the attack of vessels at anchor or in motion, but it is in 
the latter service, either in a rough sea or smooth water, that 



284 

its peculiar advantages are most apparent. It has been ap- 
proved by our naval authorities, and is about to be issued 
to some of Her Majesty's ships. 
seSlfinmaneuv- -^ u 0T & ev to maneuver this torpedo to advantage, Com- 
t')?f d? rvey ' ssea man( 3er Harvey prefers a high speed. He is of opinion that 
it cannot act well at a less speed than six knots an hour. 
This fact has an important bearing in limiting its use, es- 
pecially at night and in narrow waters. 

The following observations, on the subject of outrigger 
torpedoes, are extracted from the Report of the Committee on 
Floating Obstructions, published in 1868 : 
outrigger tor- " The success which appears to have attended the use of 

pedoes. 

torpedoes as a means of attack by the Americans, led the 
committee, at an early stage of their labors, to devote con- 
siderable attention to the plans which were submitted for 
their consideration by Captain H. H. Doty and others, for 
projecting torpedoes from the bows of small steam -vessels 
by means of outrigger fittings. 

" The plans suggested for the arrangement of outrigger 
torpedo steam-ships, among which the most efficient appears 
to be that proposed by Captain Doty, all involve the appli- 
cation of special machinery and fittings for the vessel, of 
more or less complicated and costly character, and it ap- 
peared to the committee, upon a careful consideration of 
the subject, that the objects for which the various mechani- 
cal appliances were designed could be sufficiently attained 
by easily extemporized devices of a comparatively very 
simple nature, readily adaptable to the many varieties of 
small vessels propelled by steam which are now constantly 
employed in all ports and rivers frequented by shipping. 
F } tt }^ s ^ sug ' "In March, 1865, the committee submitted to the sec- 
retary of state for war, plans for applying extemporized 
outrigger fittings to small steam-vessels, and since that 
time they have endeavored to ascertain experimentally, with 
the assistance of the captain of Her Majesty's ship "Excel- 
lent," at Portsmouth, whether any obstacles presented 
themselves to the rapid application and ready manipulation 
of such outrigger fittings. Another object of their experi- 
ments has been to ascertain whether a torpedo containing 
a charge of gunpowder or gun-cotton, calculated to produce 
seriously destructive effects when exploded in close prox- 
imity to a ship's bottom, could be fired from a small vessel 
such as a steam-launch, if attached to the end of an outrigger 
spar, without risk of injury to the attacking vessel and her 
crew. The conclusions which the committee believe they are 
warranted in drawing from these experiments are as follows : 



gestedbythe com 
mittee, 



285 

"(1.) One hundred pounds of gunpowder, inclosed inasuffi- 
ciently strong case for the proper development of its destruc- 
tive action, can be manipulated with sufficient ease when at- 
tached to the end of a spar projected 25 feet from the bows 
of a steam-launch, and fitted with, the gear described at 
page 151 and Plate XXXVIII, page 144. 

" (2.) A charge of 25 pounds of compressed gun-cotton, 
which may be relied upon to produce a destructive effect 
equal to that of 100 pounds of powder, furnishes a con- 
siderably lighter and less bulky torpedo than the latter, 
and is therefore decidedly the most convenient for boat 
service. 

" (3.) Either of the aboye charges may be exploded from 
a steam-launch, with safety to its crew and engine, if sub- 
merged at a depth of 10 feet below the surface, and fired 
at a horizontal distance of 20 feet from the launch. For this 
purpose the outrigger spar should project about 23 feet from 
the vessel. 

" Some experiments are still needed for the purpose of 
determining whether, when the torpedo has been lowered 
and the outrigger spar fixed at the proper angle, the launch 
may be navigated over a moderate distance of water with- 
out difficulty. 

"Captain A. W. A. Hood, E. IS"., of Her Majesty's ship Fittings for gign 

3ill(l WucllG" uOciT..^ 

" Excellent," has instituted some additional instructive ex- suggested by ca P - 

. . t tain Hood. 

periments for the purpose of ascertaining whether much 
smaller craft, such, for example, as gigs or whale-boats, can 
be safely and effectively applied as outrigger torpedo boats, 
and the conclusion to which he has been led is, that charges 
exceeding 40 pounds of powder, submerged at a depth of 
10 feet, cannot be exploded with safety from a 30 feet gig 
at a horizontal distance of 14 feet. 

" Though a 40-pounds charge, exploded at such a depth size of charge 
of immersion, might prove effective if in absolute contact 
with a ship, yet the committee are of opinion that the uncer- 
tainty which would attend the attempt to secure such con 
tact in the various contingencies of actual service must 
inevitably lead to failures, as it repeatedly did in the Ameri- 
can experience. For this reason they consider that 100 
pounds of gunpowder, or its equivalent in gun-cotton, is the 
least charge that should be employed. The explosion of 
such serviceable charges within a horizontal distance of 14 
feet from the operating boat was never contemplated by 
the committee, but it is evident that these charges may be 
exploded with safety from any ship of war's boat capable 
of projecting a torpedo, at the extremity of an outrigger, to 
a horizontal distance of not less than 20 feet. 



286 



Rigging-out 
paratua. 



Simplicity 
manipulation 
sintial. 



Simplicity ir 
voltaic arrange 
merits essential. 



>- " Captain Hood has devised a very convenient arrange- 
ment for handling outriggers in small boats, which has the 
advantage of enabling a second torpedo to be brought 
very readily into action. Though no explosions have 
been made with 100-pound charges attached to this appa- 
ratus from boats smaller than a launch, the committee have 
reason to believe that it can be easily adapted for employ- 
ment with such torpedoes, projected by outriggers of suita- 
ble length, from most of the boats carried by ships of war. 
In determining, therefore, the class of boat to which the 
outrigger apparatus should be fitted, it will only be necessary 
to select that which is best adapted for this service by its 
ability to carry the outrigger with ease, its speed and handi- 
ness, and by such other qualities as may be most suitable 
to the particular time and place of attack, whether it be by 
day or night, in a harbor or river, or in the open sea. 
) "The implements and manipulations connected with the 
explosion of outrigger torpedoes need only be of the most 
simple kind. Many plans have come to the notice of the 
committee for exploding this class of torpedoes by mechan- 
ical agency ; thus it has been proposed to apply friction 
tubes to their explosion, a method of firing which embraces 
several elements of uncertainty 5 various mechanical arrange- 
ments, (some of which appear to have been used by the 
Americans,) to be fitted into the heads of the torpedoes, and 
to explode upon collision with the ship's side, have also 
been suggested, that of Mr. 0. A. McEvoy being decidedly 
the best of this class of contrivances, but the committee 
consider that any mechanical arrangement for explosion by 
a blow must involve elements of danger or uncertainty: 
either the torpedo is liable to accidental explosion from a 
blow or fall in the course of the manipulation' to be per- 
formed after the "exploder" has been fixed into it, or the 
latter must be provided' with a safety- guard — the removal 
of which at the last moment may be neglected ; moreover, 
the employment of such an arrangement would necessarily 
limit the direction from which a ship could be attacked with 
a prospect of success. 

" The great simplicity to which the voltaic arrangements, 
required for boat service, have been reduced by the experi- 
ments conducted at Woolwich during last year under Mr. 
Abel's direction, has placed beyond doubt the advisability 
of exploding outrigger torpedoes exclusively by electrical 
agency. The simple pile battery, which is readily con- 
structed and put into working order by seamen after a very 
brief instruction, is prepared from materials everywhere at 



287 

band, has no special fittings whatever, remains in contin- 
uous working order for at least 24 hours, and may be used 
in open boats in any weather. A small length of covered 
wire is all that is specially required in addition to this bat- 
tery and the electric fuses for exploding the torpedoes, and 
even the coated wire and fuses, suitable for this simple boat 
equipment, may be extemporized on board ship. The only 
operation to be performed by the man in charge of the boat 
battery, in order to explode the torpedo upon receipt of the 
word of command, is to touch a metal plate on the battery 
with the end of the conducting-wire which he holds in his 
hand ; but if it be desired to render the firing of the torpedo 
quite independent of any operator, and also to insure its 
explosion at the instant of its collision with the ship's side, 
it should be fitted with the electrical percussion-fuse, devised 
for that purpose by Mr. Abel. This fuse, which is perfectly 
harmless unless placed in an electric circuity may be fitted 
to the torpedoes either in the boat or previously to their 
being placed on board. Just before the torpedo is lowered 
into the water, or before the outrigger is projected from the 
bows, one end of a conducting-wire is screwed into the fuse; 
as the boat approaches the vessel to be attacked, the other 
end of this conducting-wire is attached to tk$ battery, (which 
is already connected to earth,) and the torpedo is then ready 
to be fired by collision with the ship. 

" The committee entertain a strong opinion that the sim- 
ple system of applying torpedoes by means of outriggers 
referred to in the preceding paragraphs, if carried out by 
men well trained in the management of the outrigger boat 
and its fittings, under cover of the night, is likely to prove 
a most formidable means of attack. 

a It was deemed proper, however, to submit to actual experi- Experiments to 
ment an expedient of this kind, suitable for the use of boats 
of ships of war; and on the loth of May, 1866, a trial was 
made by the officers of Her Majesty's ship " Excellent," in 
concert with the committee. A small spar was inclined 
over the stem of the launch, so that the charge at its ex- 
tremity was at the horizontal distance of 23 feet from the 
boat, and 6 feet below the surface of the water. The charge 
was inclosed in a J-inch wrought iron case, and consisted of 
9 pounds 10 ounces of gun-cotton, which is equivalent to 
about 40 pounds of gunpowder. The boat was placed only 
6 to 8 feet from, and holding the charge nearly in contact 
with the bow of the "America" frigate; ignition was effected 
by electricity. The explosion tore away 15 feet of the ship's 
outer planking, laying bare 11 timbers, starting back an iron 



288 

knee and an inner plank, and showing daylight through the 
bottom, the oblique thickness of which at that spot was 30 
inches. The launch, however, did not suffer in the least ; 
the outrigger was broken 6 feet from the charge, where an 
iron rod, bearing the torpedo, had been lashed, but the 
three or four turns of spun-yarn, employed as a slight lash- 
ing to retain the spar in position, remained undisturbed, 
showing that no strain had been experienced by the boat. 

"To test the probable effect on the operating vessel more 
thoroughly, a second experiment was made, in which the 
launch was placed with the outrigger at right angles to and 
the charge in contact with the sunken " America," so that 
the boat might receive the fall shock of the recoil due to 
the explosion. The charge consisted of 74 pounds of gun- 
powder inclosed in a strengthened barricoe, ignition being 
effected by a friction tube. The horizontal distance of the 
charge from the boat was 19 feet 8} inches, and its depth 
below the surface was increased to 11 feet. The explosion 
did not in any way affect the boat, or the lashings and guys 
of the outrigger, but the outer end of the spar was broken 
off at a weak point about 8 feet from the charge. 

" On the 4th April, 1867, a further experiment was made 
against the sunken frigate "America,'" with a launch fitted 
with an outrigger torpedo. The only special fitting made for 
the boat was a movable iron crutch on the stem-head, to 
receive a spar 6 inches in diameter and of 30 feet in length. 
The inner end of the spar had an iron hoop with three eyes 
for small heel-tackles ; the outer end had hooped on it a 4- 
foot rod of round iron, 1 J inches in diameter, to which the 
torpedo was attached ; when required for use the crutch 
was fastened on the stem, and the outrigger launched 
through it, leaving 6 or 8 feet of the spar inboard. The 
outrigger was inclined at such an angle as submerged the 
torpedo about 10 feet beneath the surface, and 13 feet 9 
inches to 17 feet 6 inches horizontally from the boat at the 
water-line, and was confined in this position by three 
small heel-tackles inboard, and externally by a martingale. 
Charges of 50 pounds and 100 pounds of gunpowder, and 
21 pounds of compressed gun-cotton, which is equivalent to 
about 80 pounds of gunpowder, were employed ; these were 
confined in wrought-iron cases J-inch thick, and were ex- 
ploded by electricity. The boat was in each case secured in 
position with the outrigger at right angles with and a few 
feet from the bottom of the sunken ship. At each explosion 
the spar was broken off at a weak point, some 6 to 13} feet 
from the outer end, but when the torpedo was projected to 



289 

a suitable distance from tlie stem, no injury whatever was 
sustained by the boat or its fittings, and only a small 
quantity of water was shipped. On the 20th of December, 
1867, these results were confirmed by the explosion of a 
100-pound charge immersed 10 feet, and projected by an 
outrigger in a line with the keel, from the side of the bow of a 
steam-launch, to a horizontal distance of 23 feet 10 inches 
from the stem at the water-line; no injury whatever beiug 
sustained by the boat or the machinery. 

" To determine the limits of the destructive results to be ^^J f p e ^ 
anticipated from similar charges exploded at increased depths °. f powder at va- 

1 e» x z nous depths and 

of immersion, two 100-pound gunpowder torpedoes were, in distances. 
July, 1808, fired from outriggers projected from a launch to 
a depth of 20 feet, at a horizontal distance from the stem 
at the water-line of 22 feet 4 inches and 17 feet 6 inches 
respectively. In neither case was the launch injured, though 
sufficient water fell in-board from the column thrown up by 
the nearer explosion to have swamped the boat, had not the 
fore part been protected by a sloping canvas cover which 
extended to 15 feet abaft the stem. The depth of greatest 
effect of 100-pound charges is estimated to be less than 15 
feet, and the lateral destructive action of a serious nature 
to be anticipated is computed to extend over an area of 9J 
feet radius; but it is supposed that a minor destructive 
effort may extend beyond that distance sufficient to do in- 
jury to boats. These experiments tend to confirm the pre- 
vious estimations of the limited extent of the destructive 
area, while they show that the falling water must also be 
taken into consideration in determining the maximum dis- 
tance at which torpedoes can be exploded from open boats 
with safety to the operators. 

" With a view to the application of outrigger torpedoes sizes of boats 

L L oo r most suitable for 

to the smaller boats of ships of war, a series of experiments outrigger torpedr 
were conducted with a 27-foot whale-boat, and a 30-foot 
gig, fitted with outriggers projecting from the broad part 
of their bows. These side outriggers were found very con- 
venient for carrying and handling torpedoes in light boats, 
the weight being thrown further aft, and the outriggers 
being manipulated, without any movement of the crew, by 
persons in the stern sheets. A canvass awning was stretched 
over the fore part of the boat to deflect any falling water 
raised by the explosion. The ignition was in all cases ef- 
fected by electricity. The length of the outriggers employed 
in these experiments did not admit of the explosion of the 
torpedo at a greater horizontal distance than 15 feet 1J 
inches, which, with an immersion of 9 feet, was found inade- 
10 



service. 



290 

.quate to the safety of the boat and crew with a greater 
charge than 40 pounds of gunpowder. Though this charge 
would suffice for the destruction of a ship of war, if exploded 
in absolute contact, the difficulties of insuring this in actual 
service, would render it inexpedient to risk undecided re- 
sults by the employment of such a doubtful charge. If four- 
oared gigs cannot be fitted to carry outriggers capable of 
projecting 100-pound torpedoes to a horizontal distance of 
20 feet, their application to torpedo service must be very 
limited. The means, however, devised for carrying side 
outriggers in gigs, are equally applicable to galleys and 
cutters, and there is no reason why these boats should not 
project serviceable charges to safe distances. 

" These experiments show that outrigger torpedo appli- 
ances, to project destructive charges, can be employed in 
any ordinary ship's boat capable of carrying a spar of suffi- 
cient length, with perfect safety to the boat and crew. 

"A series of torpedo-boat experiments was therefore con- 
ducted by the officers of Her Majesty's ship "Excellent,'' at the 
suggestion of the committee. By these it was demonstrated 
that 100 pounds of gunpowder and 21 pounds of gun-cotton 
can be exploded with perfect safety to the boat and crew, from 
the extremity of an outrigger projected from the bow, at 
such an angle that when the charge is immersed 10 feet 
beneath the surface its horizontal distance from the stem at 
the water-line shall be 20 feet. A charge of 40 pounds of 
gunpowder, immersed 10 J feet, was also exploded with 
safety from a four-oared gig with the crew r embarked, at the 
horizontal distance of 14 feet; but a 50-pound charge im- 
mersed 9 feet, and exploded at a horizontal distance of 15 
feet 1J inches from a whale-boat, swamped the boat. These 
distances were much less than were at any time contem- 
plated by the committee as calculated to secure immunity 
to the operating vessel, while the uncertainty of securing, 
in actual warfare, the absolute contact essential to the 
destruction of an enemy's ship by the explosion of such 
small charges must preclude their employment on service. 

" The committee are of opinion that outriggers sufficiently 
long to project 100-pound charges to a horizontal distance 
of 20 feet may be carried in boats of much smaller capacity 
than launches; but whether fittings can be applied to four- 
oared gigs, by which they can do so, is yet a matter for ex- 
periment. The best means of projecting outriggers from 
steamships of various sizes, and of maintaining them in posi- 
tion at different speeds, and their influence on the steering 



291 

capabilities of the vessels, are problems which have yet to 
be submitted to experimental investigation," 

As regards the second class, or projectile torpedoes, one of w ^££*£ d , s a h ?jJ 
the most promising is that invented by Messrs. Lupin and tor P edo - 
Whitehead. A considerable amount of secrecy has been 
observed with reference to this machine, but the following, 
as far as can be ascertained, is a description of it : 

It is fusiform in shape, and is provided with projections construction. 
resembling fins and some kind of rudder, by means of which 
it may be set to run in any particular direction, and at the 
same time the depth at which it is to move below the surface 
of the water is regulated. The fins also serve to guide it 
in passing out of the tube through which it is discharged 
into the sea. Motive-power is given by means of com- 
pressed air, which is made to turn a four-bladed screw pro- 
peller. The speed obtained is about eight and a half knots 
an hour. Direction is given to the torpedo by means of an 
iron tube fitted into a vessel in such a position as to dis- 
charge it at a considerable depth below the surface of the 
water. The tube constructed in Her Majesty ? s ship Oberon, 
for experiments tried with this torpedo last autumn at 
Sheerness, was 2 feet in diameter, 28 feet long, and di- 
rected horizontally through the bow : its outer extremity 
was covered by a metal cap. The tube was divided into two 
portions, and was provided with two vertical sluices to keep 
the water out. 

The rear sluices having been opened, the torpedo is. Mode of project 
passed into the tube on rollers; the rear sluice is then mg ° rpe 
closed, the front one opened, and the cap covering the outer 
extremity of the tube having been removed, the torpedo is 
expelled from the ship by means of a piston; during this 
process the fins serve to prevent any turning motion by 
bearing upon four rails, the upper and under ones being 
provided with friction rollers placed within the tube to serve 
as guides for this purpose. As it passes out a tripper 
catches against a stud in the tube and puts in action the 
propelling power. Direction is given, or, in other words, 
aim is taken by moving the ship herself as required. 

The charge, which may be of gunpowder, gun-cotton, or Position 
any other explosive, is carried in a chamber in the head of charge * 
the torpedo, and ignition is effected by means of a percus- , 
ssion fuse. 

Numerous experiments were tried during the autumn of Experiments to 
1870 with torpedoes of this nature without an explosive pedo. e 
charge, to ascertain their capacity to move at given depths 
below, and in a given direction through the water, and these 



4! on 



292 

Laving proved fairly successful, au experiment with a 
loaded torpedo was decided ou and carried out at Sheerness 
on the 8th of October, 1870. The charge used on this occa- 
sion was 67 pounds of gun-cotton; tbe torpedo was dis- 
charged from a distance of about 150 yards at an old hulk 
called the Aigle, moored at the month of the Medway ; the 
hulk was struck and sank immediately. The explosion 
threw up a column of spray and smoke mixed with coal- 
dust to a height of about 70 feet. The spray wa£ perfectly 
distinct from the smoke and coal-dust, and proceeded from 
the water disturbed outside the vessel's hull ; the smoke 
and coal-dust being probably due to the explosion acting- 
inwards, through the vessel's side, and the column of gas 
driven through the interior of the ship. The two sec- 
tions of the column, viz, the white spray and black smoke 
and coal-dust were entirely distinct from each other and 
not mingled in any way. 
Effect of expio- rp| je damage done by this explosion consisted of a clear hole 
on the side struck, (the starboard side,) 26 feet long and 9 
feet in depth, and extending down to the keel; about 4 feet 
of the planking above this hole was broken and the copper 
more or less torn off for a length of about 40 feet. Inside 
the hulk half the main deck, up to the mizen hatchway, was 
carried away, and the remainder much torn and injured. 
On the upper deck the planks round the hole, left by the 
removal of the mizen-mast were displaced and forced up- 
wards for a distance of about 12 feet. The planking on the 
port side of the vessel was blown outward for a length of 
16 feet, and to a depth of 2 feet, while it was shaken for a 
further distance, and the copper more or less stripped over 
an area extending considerably beyond the space mentioned. 
In considering the extent of damage done, it must be borne 
in mind that the Aigle was an old wooden ship, probably 
somewhat rotten, and it is scarcely likely that this amount 
of damage would have occurred had the same torpedo been 
exploded against the side of a ship so strongly built as a 
modern iron-clad. This is, however, a question for the con- 
sideration of naval architects. 
torpedo A small torpedo of the same class, 14 feet long, 14 inches 
in diameter, and carrying a charge of 18 pounds of giyoxa- 
line, was subsequently fired from an apparatus suspended 
beneath a boat which was placed at a distance of about 150 
yards from the Aigle, and directed at some netting arranged 
to protect the vessel against an attack of this nature. Tbe 
torpedo was fired by contact with the netting, but did no 



fired from boat. 



293 

apparent injury to the ship. The netting was hung about 
1G feet clear of the vessel's side. 

This torpedo must necessarily start with a low velocity, flu ^"e ict of g c i?- 
and even at its best, as at present arranged, does not attain rents - &c - 
a speed of more than eight miles an hour, which would ren- 
der it very liable to disturbance from the effects of currents. 
This, combined with the extreme care and the amount of 
trouble which seemed to be necessary in taking aim from 
a distance of only 150 yards, in perfectly smooth water, in 
the experiment above described, seems to indicate that there 
would be a considerable amount of uncertainty in direction 
at the distance of 800 yards at sea, at which the inventors 
claim that it is practically effective. Destruction would no 
doubt result from striking a ship with this or any other tor- 
pedo ; but the great difficulty would seem to be experienced 
in attempting to hit a ship, with this or any other known 
projectile torpedo, at a serviceable distance with any approach 
to certainty. 

Mr. Lancaster, the gun-maker, made a proposition to the J°J pe b doeb n .j^t 
Government some years ago, to propel a torpedo through composition. 
the water, by means of rocket composition carried in the 
body of the apparatus. His ideas, however, were not 
approved, and consequently were never worked out. More 
recently Mr. Quick, engineer of the royal navy, has brought 
forward a similar proposition, and an experiment has been 
recommended by the royal engineer committee to test its 
value. This experiment has not yet been carried out. 

Mr. Quick's idea seems to be similar to that of Messrs. 
Lupin and 'Whitehead, the chief difference being in the pro- 
pelling agent, rocket composition, suggested in the former, 
instead of compressed air, as in the latter case. 

Should efficient projectile torpedoes be devised they might use of projectile 
be used against ships at anchor, or perhaps moving slowly, 
also for the destruction of obstructions extending to any con- 
siderable depth below the surface of the water. They do not 
seem applicable to the attack of ponton-bridges or booms as 
the chance of striking such objects would be comparatively 
small, unless the power of regulating the depth at which they 
would move below the surface is capable of being very 
nicely adjusted. Their direction with such a comparatively 
low velocity as can be attained, is so easily disturbed by 
currents and other conflicting causes, that they would seem 
applicable dnly to the attack of objects presenting a con- 
siderable breadth of front, and the chance of hitting a ship 
in motion, at a distance of even one or two hundred yards, 
would appear to be extremely small. 



294 
Drifting torpe- Among the various devices suggested at different times 

does. ° °° 

for the third class or drifting torpedoes, the most promising 
seem to be those designed by Captain McEvoy, of the late 
confederate torpedo service, and by Lieutenant J. F. Lewis, 
E. E. 

McEvoy's drift- The following description of McEvoy's self-acting drifting 
torpedo, is extracted from the report of the committee on 
floating obstructions, published in 1868 : 

construction. " The torpedo case is to be suspended from a float, and 
permitted to drift down upon an enemy's floating bridge in a 
river, or against a vessel at anchor, but specially suitable 
for the former purpose. 

" On the top of the exterior, protected by iron bars, is a 
sensitive percussion fuse, with a hammer retained at full 
cock by a lever, which is acted upon by the threads of a 
screw. To this screw is attached a many-bladed screw pro- 
pellor of sheet tin, balanced by a fan or rudder blade on the 
opposite extremity, the Avhole pivoting round the percussion 
fuse, and occupying little space. 

Mode of action. " So long as the torpedo continues to drift, the apparatus 
on its top will be unaffected by the current, but as soon as 
the motion of the torpedo is interrupted, the current run- 
ning past will act on the fan or rudder blade and turn the 
screw propeller to the current, when a given number of 
turns will liberate the hammer and cause explosion." 

Fig. Ill shows the general design of the apparatus : A is 
the sensitive fuse, B the hammer, retained at full cock by 
pressure against the catch K, which works in the threads 
of the screw ; C is the fan to turn the screw propeller, 
pivoted round the fuse A to the current when the torpedo 
ceases to drift : D is the screw propeller of sheet tin, to be 
revolved by the current when the torpedo fouls anything 
and ceases to drift; this action would disengage the catch 
K and allow the hammer to fall and ignite the sensitive 
fuse A; E E are circular . guards to protect the igniting 
apparatus, F F iron slings, G the suspension rod, and H 
the surface buoy. This figure is copied from the report of 
the committee on floating obstructions : 

Lewis's drifting The following description of Lieutenant Lewis's self-acting 
drifting torpedo, is extracted from the report of the committee 
on floating obstructio?is : 

u This is a contrivance for projecting drifting torpedoes 
under booms or other floating obstructions employed for the 
defense of ships at anchor. 

construction. " The torpedo consists of a cubical box capable of contain- 
ing 55 pounds of powder, and furnished with five detonat- 
ing fuses in one of its sides. 



Fig. 111. 

E I)riftistf/ Biboy, rff i ./rn, tha <Sxirfh/&. 




295 

"This torpedo is attached to one side of a beam, and 
within six inches of one extremity— the beam being 20 feet 
long and 7 inches square. To the opposite side of the same 
end of the beam a 60-pound iron weight, resting in a shoe, 
is attached by a long iron rod which reaches to the other 
extremity of the beam, and is there connected to a bell-crank 
lever and spring, a pressure on which detaches the weight, 
A chain 18 feet long connects the weight loosely with the 
upper end of the beam, and another chain, 9 feet 6 inches 
long, connects it with a point more than two feet below the 
center of the beam. The whole arrangement floats nearly 
vertically with the top of the beam, just above the surface 
of the water. 

"When the apparatus drifts against the boom or other Mode of action, 
obstruction, the spring or lever at the upper extremity is 
pressed down, thus raising the long iron rod and releasing 
the weight, which, falling, becomes suspended by the two 
chains, throwing the beam into an inclined position. The 
weight of this mass of iron and the chain suspending it 
are suddenly brought to bear on the top of the beam, drag- 
ging it under water and clear of the floating obstructions, 
at the same time the lower end, released, from the weight, 
rises and the whole apparatus is carried forward by the 
current against the side of the vessel, on striking which the 
torpedo explodes." 

Fig. 112 shows the general form of the apparatus j (a) is 
the box containing the charge ; (b) the beam to which it is 
attached ; (c) the 60-pound weight resting on the shoe (d; ) 
(e) is the iron rod connecting it to the bell-crank lever and 
spring (/;) (g) and (h) are the two chains connecting the 
weight to the beam. 

Machines of this nature might be used for the attack of A . Nature of opera- 

° tions to which 

ponton-bridges, booms, and obstructions generally ; those drifting torpedoes 

077 ° ^ ' are applicable. 

exhibiting a broad face being the most likely to be injured by 
them. Being dependent on the force and direction of cur- 
rents, it would be necessary to study both carefully before 
proceeding to undertake any operation involving their use, 
and in a tide- way it should be borne in mind that if carried 
in one direction, toward an enemy for example, by the flood 
tide they would, unless expended, return toward their 
friends with the ebb. The two forms described are not very 
expensive or difficult of construction ; if to be used, there- 
fore, it would seem desirable to employ very large numbers, 
as, from their nature, it is probable that a large proportion 
would prove ineffective. The consternation and confusion 
described in Commander Barnes's book on Submarine War- 



296 

fare j as having occurred among the British ships in the 
Delaware on the 7th of January, 1778, when a number of 

%. in. 



--—~-—-.<?urfi 



J JUd7ace of 




: 



m 



A 



kegs, filled with powder and arranged to be fired on con- 
tact by a simple gunlock, were drifted down to attack them, 



297 

shows bow much maybe done with extremely rough means. 
Au attack by drifting torpedoes in large numbers is there- 
fore quite applicable to certain cases, and may be success- 
fully employed. 



cotton 



Cases. 



CHAPTER XVI. 

APPROVED FORMS OF APPARATUS. 

A considerable advance has been made, since the first of 
these papers was written in January, 1869, in determining 
the nature of the explosive, size and construction of cases, 
form of fuse, nature and dimensions of voltaic batteries, 
forms of electrical cables, and other similar details, and it 
is proposed to describe briefly what, at the present moment, 
may be taken as most appropriate for submarine mining 
purposes. 
Explosive gun- The explosive should be compressed gun-cotton, fired with 
a detonating fuse; where gun-cotton is not procurable, 
gunpowder fired, if possible, with a detonating fuse may be 
used. 

The cases should be of wrought iron, with a cast-iron 
loading-hole, which also serves to receive the fuse or circuit- 
closer. Oases to contain charges of the following sizes are 
recommended, viz: 100 pounds, 250 pounds, 500 pounds, 
and 1,000 pounds. 
one hundred The general design and dimensions of the 100-pound case 

pound case, con- 

mction and di- are shown in section in Fig. 113. It consists of a wrought- 
iron cylinder (a) of No. 12 B. W. G. iron plate, riveted ; the 
upper end (b) to be dished and of the same thickness of 
metal ; (c) is the mouth-piece, riveted directly to the cylin- 
drical iron plate of the body ; this opening is circular, 6 
inches in diameter, and, serves as a loading-hole and for the 
introduction of a circuit-closer of Mathieson's form, which 
is arranged to be placed within the case; (d) is a screw- 
piece to keep everything water-tight, as described in page 
90, Fig. 33; (e) is a wooden jacket of fir, conical in form, 
to protect the iron cylinder from injury when subjected 
to blows from friendly passing ships. The wood of which 
the jacket is composed should be well seasoned, thoroughly 
saturated in tar, and subsequently painted to keep the water 
as much as possible from entering into its pores after sub- 
mersion, so that tne buoyancy of the wooden jacket may 
increase the flotation. The case is intended essentially for 
a contact charge, and a maximum of buoyancy is absolutely 
necessary. The wooden jacket is bound together by iron 
bands and provided with a ring (/) at the top, from which 
to suspend the case for mooring purposes. The whole of 
the iron work of the case should be painted two coats, and 
tested up to a pressure of 10 pounds on the square inch, 



mentions. 



299 

. ^dually increasing from within. The calculated weight 

of this case, complete with circuit closer and charge, is 

Fig. 113. 



sri 




Sectivru. 




-Bottom Flam. 
about 470 pounds, and its available buoyancy, that is to say 5 
actual power of flotation, about 140 pounds. 



300 



and W fift hun u r nd ^ ne & enera ^ design and dimensions of the 250-pound case 
case, construction are shown in section in Fig. 114. The body consists of A- 

and dimensions. ° ^ l " 

inch best boiler- plate iron, riveted, with dished ends. The 
size and construction of the mouth-piece is similar to that 



Mf. 11*. 




Sec&ow. 

of the 100 pound case, so that the fuses, &c, may be inter- 
changeable. The whole of the iron work should be painted 
two coats, and tested to a pressure of 30 pounds on the 
square inch, gradually increasing from within. The moor- 
ing chains are attached by eyes to wrought-iron bands 



301 

shrunk on and screwed to the body by coupling screws, as 
shown in the figure. The charge of 250 pounds renders it 
applicable for the destruction of a vessel without absolute 
contact; it may, however, be necessary, in certain cases, to 
employ it as a contact mine, and when used as such, a 
wooden jacket, as shown in the figure, must be added to 
protect the case from injury by collision with friendly ves- 
sels. Its calculated weight, complete with charge, and with- 
out the wooden jacket, is about 520 pounds, and its avail- 
able buoyancy, (actual power of flotation,) is about 80 
pounds. Fig. 115 shows a plan of the bottom of this case, 
including the wooden jacket. 

Fig, 115. 




Bottom Flan: 

In order, therefore, to convert this into a buoyant mine, 
additional flotation must be given by the attachment of 
buoyant bodies thereto. The amount of flotation to be 
added would involve conditions, dependent on the length of 
mooring cable necessary and the nature of the current in 
which the mine is to be placed. The wooden jacket adds 
to a certain extent to the buoyancy, but it must be borne 



302 



mensions. 



in mind that, even with every precaution, the wood becomes 
more or less saturated after submersion for any considerable 
time, and only half the buoyancy due to this outer casing 
should, on this account, be included in calculating for flota- 
tion to be given under any particular circumstances. 

The general design and dimensions of the 500-pound case 

in ] 

Fig. 



Five hundred 
poimd case, con- 
struction and di-'are shown in section in Fig. 116. The body is formed of J- 



116. 




inch best iron boiler-plate. The ends are dished, au the 



mouth -piece and 



for the attachment of the 



One thousand 
pound case, cor 



303 

moorings are precisely similar in form to that of the 250- 
pound case. The whole of the iron- work should be painted 
two coats; the case should he tested to a pressure of 40 
pounds on the square inch, gradually increasing from within. 
The calculated weight of the case, with charge complete, is 
about 1,000 pounds ; this exceeds the total buoyancy by 
about 190 pounds; it has, therefore, no floating power, and 
if required to be floated np from the bottom the necessary 
buoyancy must be attached. 

No definite pattern of case to contain a charge of 1,000 
pounds has yet been made; it should, however, be similar JJ^J^J aud di 
in form to the 500-pound case, and be composed of J-inch 
best iron boiler-plate, and of such cubic space as to contain 
the requisite charge, viz, -J feet 9 inches by 3 feet 4 inches, 
not including the dish of the ends. The mouth-piece 
should be the same as before, iu order that the fuse-pieces 
may be interchangeable; the attachments for the moorings 
should be similar to those of the 500 pound case, but of pro- 
portionately larger dimensions. 

The dimensions of all these cases are calculated for com- . Above , di , men : 

sions calculated 

pressed gun-cotton, and their thickness is not sufficient to de- for compressed 

A ' gun-cotton. 

velop the maximum explosive force of gunpowder; if, there- 
fore, this latter explosive be used, detonating fuses and sev- 
eral centers of ignition must be employed. The cubic space 
occupied by a given charge of gunpowder is slightly less 
than that required for an equal weight of compressed gun- 
cotton; for practical purposes, however, the cases described 
may be taken as the same for both. 

The best special mooring apparatus for general purposes ra JJg° r musXm 
seems to be the mushroom sinker, somewhat similar to that anchor - 
shown in Fig. 20, and described in pages 72 and 73. Its 
weight would depend upon the buoyancy to be overcome, 
and would generally be from five hundred-weight, upward. 
Ordinary mooring-chains and hemp cables may generally 
be employed in connecting the charges or circuit-closers 
' with the sinkers. Where there is any tendency to twist, a 
wire cable is the best to counteract it. Any considerable 
amount of twisting must be checked, as it is liable to en- 
tangle the moorings and to rub and injure the electric cables. 
The strength of the chains or cables employed must depend 
upon the amount of buoyancy possessed by the mine or 
circuit-closer. The cable connected w T ith the circuit-closer 
would also frequently be subjected to a severe strain if 
caught by the paddles, screws, &c, of a friendly vessel pass- 
ing over the mine. For this reason stronger cables, both 
electric and mooring, must be provided at that point. 



304 

£££■* torpefio F° r mechanical ignition Abel's torpedo primer, described 

at page 88, and shown in Figs. 26 and 27, may be used. 
fafe atinum wire ^ or electrical ignition a platinum wire fuse, primed with 
fulminate of mercury, somewhat similar to that shown in 
Fig. 51, page 133, seems most suitable. 

Mr. Abel is now engaged in experiments with a new form 
of tension-fuse for submarine mining purposes, but as yet it 
is impossible to decide whether it will eventually supersede 
the platinum wire fuse or not. 

Electric cables. The electric cables which seem best suited for submarine 
mining-service, are the following : 

smgie cable. Tlie s i ng i e cable, to consist of a strand of four No. 20 B. 
W. G. copper wires tinned, insulated with vulcanized In- 
dia rubber to a diameter of T 2 6 4 o inch, over which a layer 
of felt is wound; the whole is then submitted to a tempera- 
ture of about 300° F. to consolidate the di- electric. Over 
the core thus formed a covering of tarred hemp should 
be wound on spirally, followed by 8 No. 13 galvanized iron 
wires, each wire separately covered with tarred hemp. The 
whole to be finally covered with two coatings of hemp and 
composition, (consisting of tar and some bituminous sub- 
stance,) wound on with a short twist in opposite directions. 
The external diameter of the whole would be about J inch. 
The weight of this cable would be about 20Jcwt. per nauti- 
cal mile. 

Multiple cable. The multiple cable, to consist of seven single cores, as 
above described, formed into a strand. The whole covered 
with tarred hemp, laid on spirally, subsequently with 16 No. 
9 B. W. G. galvanized iron wires, (each wire separately 
covered with tarred tape,) laid on spirally over the hemp 
covering. The whole finally covered with a layer of hemp 
and composition laid on with a short twist. The diameter 
of a multiple cable, constructed in this way, would be about 
1J inches and its weight 5 tons per nautical mile. Either 
Hoopers or Gray's patent di-electric is very suitable for 
this service. They are both combinations of vulcanized 
India rubber, which forms a very flexible covering to the 
copper conductor, and may be stored either wet or dry. It 
must, however, be kept always wet or always dry, as any 
alternation of these conditions would tend to rot the hemp 
covering and di-electric. Should it be necessary to store an 
electric cable insulated with gutta-percha, it must be kept 
under water. When so treated it may be preserved in a 
sound state for a considerable length of time. Dry air has a 
very deleterious effect upon gutta-percha, causing it to 
become brittle and crack when bent after exposure to 



305 

its influence for a comparatively short time. When gutta- 
percha cables, therefore, are to be stored, tanks must be 
provided for their reception. 

The voltaic battery temporarily adopted is Walker's, Firing-battery, 
(zinc and carbon plates in diluted sulphuric acid.) The zinc 
element consists of a plate 7J inches by 4J inches, amalga- 
mated with mercury, the carbon pole being formed of a pair 
of plates each 6£ inches by 4 J inches, connected together to 
form one element. The dimensions of the outer cell are 5 
inches bj- 2J inches and 7 inches deep. The greater depth 
of the zinc plate brings its lower extremity to the bottom of 
the outer cell, in which a small quantity of mercury is 
placed to keep the zinc amalgamated. The graphite plates 
do not reach down so far as to touch the mercury. The 
slipper generally used in this form of battery to hold the 
mercury may thus be dispensed with. They should be ar- 
ranged in a wooden frame, so that the battery-plates may 
be lifted out of the liquid when not in use. This may be 
readily done by means of a small chain, or rope and pulley. 
They need only to be lifted a very short distance, just clear 
of the diluted acid, and not absolutely out of the cell. 
This will prevent the chance of damage to the plates which 
was found to occur when they were lifted to any great 
height, by striking against the edges of the cells when sub- 
sequently lowered. 

Experiments are now being made with a large form of Le cianchg bat- 
Le Clanche battery, to ascertain whether it is not better tery ' 
than Walker's for submarine mining purposes. The 
Le Clanche battery is no doubt preferable to Walker's in 
many important respects ; its constancy, for example, is 
greatly superior, but till the experiments are completed no 
definite opinion can be given. 

For firing at will, when it is desirable to dispense with Dynamo-eiectric- 
battery power, the dynamo-electrical machine seems to be a 
the best form of instrument for submarine mining purposes. 
The size adopted as the field-service pattern for the engi- 
neer equipment, seems to be a very convenient form of in- 
strument for this work. Its weight complete, with carrying 
case and straps, is 28 pounds. 

For firing by intersection at long distances, telescopic. Telescopic fir- 
keys, somewhat similar to that described at page 194, Fig. 
82, would be required. The radius of the arc on which the 
firing-contacts are to be fixed, should be increased to a 
minimum of 36 inches, and the eye-piece of the telescope 
should be placed farther back, so as to be easily seen 
through when the hand is employed in moving the appa- 
20 



306 

ratus round in following a ship. A pair of improved instru- 
ments of this nature are now being made for the trial of 
this system. 
Matweson's cir- When a platinum wire fuse is used, a circuit-closer or 

cuit-cioser and * ' 

breaker. breaker of Mathieson's form, as described at page 209, Eig. 

87, seems to be the most generally useful instrument of 
this class. When simple contact mines are used the instru- 
ment may -be connected as a circuit-closer. When the 
mines are arranged with a detached circuit-breaker to be 
fired by the contact of a ship, with an alternative mode of 
ignition by intersection, the apparatus should be connected 
as a circuit-breaker. An improvement has recently been 
introduced into this instrument, which consists in reducing 
the number of supporting pillars and springs, with their 
corresponding connections, to three instead of four, as shown 
in Fig. 87. The reason why this instrument is so well 
adapted for use with, the platinum wire fuse is, that the 
springs produce a slight prolongation of the contacts when 
the apparatus is used as a circuit-closer, and this gives an 
almost inappreciably prolonged interval for the circulation 
of the battery-current which is desirable to produce the 
heating power necessary to fuse the fine platinum wire 
forming the fuse. 
Abeis circuit- Experiments are now being carried on with Abel's circuit- 
closer, somewhat modified on that described at page 202, 
Eig. 85, with a view to test its capabilities as compared with 
Mathieson's circuit-closer and breaker. It is probable that, 
with a tension fuse, either may be used, and no definite deci- 
sion can be made till the experiments are completed. With 
the platinum wire fuse, however, Mathieson's apparatus is 
preferable to Abel's, as the latter is at present constructed 
for the reasons already given. 
shutter signal- rj^ f orm f shutter- signaling apparatus, which seems 

iDg and firing ap- & ° L L 7 

. paratus. b es t adapted for submarine mining purposes, is that 

described at page 232, Eig. 97, in which the contacts are 
made by means of mercury-cups in place of the springs 
which were first used. Further experiments, however, are 
required with this form of instrument before it is possible 
to decide definitely whether it is the best suited for the pur- 
pose, or even whether it may be found convenient to use an 
apparatus of the shutter form at all. 



THE END. 



iistdex: 



A. 

Page. 

Action, electrical, between metals in sea-water 64 

Agents, explosive £S 

" America," Her Majesty's ship, experiments on, to determine the effect of a 

given charge 43 

Anchor, mushroom, Austrian 64 

most approved form 303 

Anchors, ordinary 84 

Astatic galvanometer 268 

B. 

Bag, gun-cotton, to surround charge, suggestion 113 

Bags, India-rubber, Captain Harding Steward's 52 

Balance, electrical, Wheatstone's 269 

Barge, mooring, Austrian, arrangement of 80 

Barrels, employment as make-shift cases 59 

Battery, voltaic, Austrian, for submarine mines 181 

Daniell's 179 

Muirhead's 180 

Varley's 180 

firing, Walker's, most approved form 305 

for use with platinum wire-fuse 172 

tension fuse 177 

Grove's 172 

and platinum fuse, experiments with 94 

defects of 98 

ignition by 172 

LeClanchd 182-305 

Marie'-Davy 179 

sand, Wollaston's : 177 

Walker's 98-172 

Batteries, quantity, tests of 253 

voltaic, testing 269 

tests of 250 

Beach, open, defense of, by submarine mines 13 

Blavier's formula to discover position of fault 260 

Boat service, torpedo outrigger for 275 

Boats, clearing channel by 271 

size most suitable for outrigger torpedoes 289 

Boiler, steam, as a makeshift case - 60 

Boom, electric cable in connection with 128 

Booms, defense of mines by , 161 

Box, testing, for connection of multiple cable 124 

Breakers, circuit, Mathieson's 208 

most approved form 306 

Bridge, electrical, Wheatstone's 269 

Buoyancy, necessary for mines moored from bottom 85 



308 
c. 

Page. 

Cable, condition of, best suited for resistance test 262 

Cable, electric, multiple, most approved form 304 

single, most approved form 304 

tests of 243 

test of electrical resistance of 247 

Cables, electric, Austrian 115 

brancb system 124 

Gray's core 118 

Hooper's core 117 

improvised 129 

in connection with, booms 128 

introduction into a fort 157 

mode of paying out 151 

multiple 119 

multiple, defects of 121 

outer protection of ordinary rope 127 

permanent joints in 137 

protection from wash of sea 154 

qualifications required 115 

Siemens', protected by copper tape 116 

multiple, tests of 246 

Case, conical, for small mechanical mines 49 

cylindrical, for large charges 50 

100 pound, description of approved form 298 

250 pound, description of approved form 300 

500 pound, description of approved form 302 

1,000 pound, description of approved form 303 

experiments on strength by floating obstruction committee 57 

form of, Austrian 51 

general form of 49 

internal, sheet-tin or India rubber 60 

must be thoroughly water-tight 60 

strength required for gunpowder and gun-cotton 60-303 

strong, required when gunpowder is used 28-113 

tests of 239 

Cases, boiler-plate iron, construction, calculated strength, &c 54 

buoyancy necessary 85 

make-shift 59-60 

materials for construction of 51 

not to be loaded in the sun or at high temperatures 54 

Catch, mooring. Austrian 63 

barbed 65 

Cell, sea, disturbing influences during test .- 256 

test for insulation by 255 

Channels., illumination of 162 

Charge, effect of, when fired under water ; general conclusions 44 

ignition of, at will 163 

maximum, to be fired with a single fuse 109 

size of 40 

approximate rule for 45 

confederate rules for 40 

experiments on, by floating obstruction committee 42 

used in destruction of wrecks in River Hoogly 42 



309 

Page. 

Charge, small, mode of mooring (37 

test to ascertain whether dry 254 

Charges submerged, examination of 77 

when visible to be disguised 83 

Circuit-breaker, Mathieson's 208 

Circuit-closer, Abel's- 201-306 

Austrian 199 

dual-electric, Mathieson's 211 

Mathieson's 204 

pendulum 211 

and breaker, most approved form 306 

Circuit-closers combined with or detached from mines 213 

mechanical 199 

when visible to be disguise d 83 

Clearing channel by small boats 271 

by submarine explosions 274 

Coils, resistance 269 

wive, of instruments must be suited to current to be conveyed 237-270 

Committee on floating obstructions, appointed 9 

Company, constitution of, for submarine mining duty ,..-... 270 

Connection, water-tight, temporary 134 

clay, 135 

Contact mines for defense against boats 219 

Cost of submarine mines, small 15 

Course of instruction at Chatham 9 

Cross-bearings, firing by 186 

Current, negative, used for testing purposes 246 

D. 
Defense by submarine mines, especially applicable to United Kingdom and 

colonies 14 

increase to, by use of submarine mines 15 

of a channel ; distribution of mines 23 

of a first-class fortress 11 

of a mercantile harbor by submarine mines 12 

of an open beach by submarine mines 13 

of an open roadstead by submarine mines 26 

of mines by booms and fishing-nets 161 

from drifters 161 

Detachment, number of, for submarine mining duty 270 

Detector galvanometer 268 

Detonating fuse, experiments with gun-cotton and glyoxaline 30 

fuses, tests of 243 

Differential galvanometer 268 

Disconnector, Anderson's 217 

electro-magnetic 217 

Mathieson's 216 

Distribution of mines for defense of a channel 23 

Drifters, defense of mines from 161 

Drifting torpedo, Lewis' « 294 

McEvoy's 294 

Drifting topedoes 275-294 

nature of operations suitable for 295 

Dummies, use of 83 

Dynamite, experiments with, against hull of frigate - 38 



310 

Page. 

Dynamo-electrical machine, Ladd's - 167 

Siemens' 165 

most approved form of 305 

E. 

Earth connections with Grove's battery and platinum fuse 94 

Effect, comparative, of gunpowder and gun-cotton fired under water with de- 
tonating fuse 35 

of charge when fired under water ; general conclusions 44 

Electric cable, multiple, most approved form 304 

single, most approved form 304 

tests of 243 

Electric cables, Austrian 115 

branch system 124 

Gray's core 118 

Hooper's core 117 

improvised 129 

in connection with booms 128 

introduction into a fort 157 

mode of paying out , 151 

multiple 119 

multiple, defects of 121 

outer protection of ordinary rope 127 

permanent joints in. 137 

protection from wash of sea , .. 154 

qualifications required 115 

Siemens', protected with copper tape 116 

Electric telegraph from fort to guard-boat 161 

Electrical balance or bridge, Wheatstone's 269 

ignition 93 

instruments used in testing 268 

machine, dynamo, description of 165 

most approved form 305 

frictional 1?0 

resistance of cable, test of 247 

submarine mines 17 

advantages and disadvantages 17 

tests 238 

value due to comparison 258 

Electro-magnetic disconnector 217 

Electrometer, reflecting 268 

Equation, personal, of observer 264 

Exploder, magnetic, Beardslee's 164 

Marcus' 168 

Wheatstone's 163 

tests of 250 

Explosive agents. 28-298 

best suited for submarine mines. 298 

Explosives, tests of 239 

Extent of fault, determination of, Lieutenant Fisher's method 266 

F. 

Fault, extent of, Lieutenant Fisher's method of determining 266 

Firing-battery, Walker's, most approved form 305 

by cross-bearings .1 286 



311 

Page. 

Firing-key and fixed telescope, use of- 198 

attached to testing-table* 224 

keys 191 

telescopic 193 

most approved form 305 

Fishing nets, defense of mines by 161 

Fish torpedo, Lupin and Whitehead's 291 

fired from boat 292 

Fleet, inferior, protection of, by submarine mines 1 13 

Formula, Blaviers, to discover position of fault 260 

Fortress, first-class, defense of 11 

Frames, projecting, carried ou vessel's bows 271 

Frictional, electrical machine 170 

tests of 250 

Frictional electricity, induction experiments 212 

Fuse, Abel's 101 

detonating 104 

precautions in testing 104 

Beardslee's 99 

Brook's 87 

chemical 87 

detonating, experiments with, to fire gun-cotton and glyoxaline 30 

electrical, high tension, extemporized 106 

Fisher's 108 

introduction into metal case 130-133 

barrel 132 

platinum wire 93-95 

advantages of 93 

battery for use with 172 

most approved form 304 

tests of 240 

with guu-cotton priming 97 

Prussian 101 

sodium or potassium 88 

surrounded with gnn-cotton 113 

tension, battery for use with 177 

tests of 242 

VonEbner's 100 

Fuses, detonating, tests of 243 

distribution of, in charge 109 

electric, for current of high tension , 99 

mechanical defects of 90 

Harding Steward's safety 91 

tests of 240 

mode of fixing, in position 113 

position of, in charge 108 

two, to be used at each center of ignition 113 

G. 

Galvanometer, astatic r 268 

detector '.. 268 

differential = 268 

reflecting 268 

sensitive, for testing purposes 245 

thermo 269 



312 

Page. 

Glyoxaline - 39 

experiments with, fired with detonating-fuse 30 

Gray's electric cable 118 

Grove's battery and plati mini fuse, experiments with 94 

defects of 98 

Guarding mines at night 161 

Gun-cotton 29 

and gunpowder, comparative effect Avhen fired under water by de- 
tonating fuse 35 

bag to surround charge ; suggestion 113 

compressed 29 

Abel's improvement in manufacture 29 

experiments with, when fired with detonating-fuse ... 30 

explosive effect of, examined theoretically 36 

most suitable for submarine mines 298 

not explosive when wet , 36 

priming for platinum- wire fuse 97 

Gunpowder and gun-cotton, comparative effect when fired under water by a 

detonating-fuse 35 

explosive effect of, examined theoretically 36 

proportion of charge as compared with other explosives 46 

use of, for submarine mines 28-298 

Gutta-percha insulation, defects of 115 

H. 

Harding Steward's improvement in mechanical mines 18 

Harvey's sea-torpedo 280 

Hooper's core 117 

I. 

Ignition by battery power. , 172 

electrical 93 

mechanical modes of 87 

of charge at will - 163 

Illumination of channels 162 

Improvements in mechanical mines, Harding Steward's 18 

India-rubber bags, Harding Steward's 52 

insulation . 116 

Induction coil 169 

effect of, in testing several joints together 250 

when frictioual electricity is used .. 121 

experiments with frictional electricity 212 

Injury to insulation, points most liable to 265 

Instruction, course of, at Chatham 9 

Instruments, coils of, must be suited to the current to be conveyed 237-270 

electrical, used in testing 268 

- testsof 239 

Insulated and water-tight joints 130 

joints, test of 248 

delicate tests by special apparatus 248 

Insulation, gutta-percha, defects of 115 

India rubber 116 

advantages and defects 220 

points where most liable to injury , 265 



313 

Page. 

Intervals to insure safety to adjoining mines 46 

Introduction of electric cables into a fort 157 

of fuse into barrel 132 

of fuse into metal case 130 133 

J. 

Joint, Beardslee's 146 

bottle, Dent's 142 

Glover's 145 

India-rubber, permanent 139 

tube, advantages and disadvantages 142 

Mathieson's 147 

for electric cable with outer protecting covering 149 

metallic, Nicoll's 142 

water-tight, clay 135 

Joints, India-rubber tube 141 

insulated and water-tight 130 

permanent in electric cables 137 

temporary, insulated 140 

water-tight and insulated, tests of 248 

K. 

Key, firing, and fixed telescope, use of 198 

for simple testing-table 224 

Keys, firing 191 

telescopic 1 193 

most approved form 305 

L. 

Lateral pressure on buoyant mines, calculation for 86 

Le Clanche" voltaic battery.../; 182-305 

Line, single, of mines, disadvantage of 22 

Lines, disadvantages of arrangement of mines in 161 

Loop-test, Varley's 258 

M. 

Machine, frictional electrical 170 

Magnetic exploder, Beardslee's 164 

Marcus' 168 

WheStstone's 163 

Materials for construction of cases 51 

for submarine mines, easily obtainable 16 

Maximum cbarge to be fired with a single fuse 109 

Mechanical circuit-closers 199 

fuses, defects of 90 

Harding Steward's safety 91 

tests of 240 

ignition 87 

submarine mines 16 

advantages of 17 

danger in submerging 18 

disadvantages of 16 

tests , 233 

Men, qualifications of, for submarine mining duty 270 

Mercantile harbor, defense of, by submarine mines 12 



314 

Page. 

Mine, ground, must be heavy » 80 

submarine, definition of 7 

Mines, circuit-closers combined with or detr.ched from '213 

contact, for defense against boats 219 

defense of, from drifters 161 

disadvantage of arrangement in lines « 161 

mode of marking position 151 

placing in position 80 

moored from bottom, buoyancy required 85 

must be guarded at night 161 

offensive, or torpedoes 9-275 

position of to be concealed 157 

submarine, American „ 8 

Austrian 8 

Chinese- - 8 

cost of, small - 15 

defensive , = 10 

electrical 17 

advantages and disadvantages 17 

intervals between to insure safety to adjoining mines 46 

materials for, easily obtainable 15 

mechanical 16 

nature of ., 16 

Russian 8 

Mooring apparatus, most approved form 303 

tests of. - 240 

Mooring, Austrian arrangement of barge -• 80 

mode of 63 

by single cable , 71 

experiments in Medway , 66-71 

extemporized S3 

faulty arrangements to be avoided 66 

fore and aft - 69 

from ponton-raft 81 

Harding Steward's, for mechanical mines 92 

ladder method 68 

operations, favorable weather necessary 76 

running gear in connection with, power of working 78 

ship's launch fitted for „ 72 

small charges, mode of 67 

to a heavy chain cable 74 

weight of 84 

with considerable rise and fall of tide , '. . 82 

with directing hawser 75 

Mortars, twin, suggestions for use in clearing channels 273 

Muddy bottom favorable for mushroom anchor 73-86 

Multiple cables, tests of 246 

Mushroom anchor, Austrian ,. 64 

sinker, most approved form 303 

N. 

Negative current used for testing purposes 246 

Nitro-gly cerine 37 

explosive effect of, examined theoretically 36 

Number of a company and detachment for submarine mining duty 270 



315 



o. 

Page. 

Obstructions, passive, combination with submarine mines 24-271 

Officers and men, qualification for submarine mining duty 270 

Outrigger torpedo fitted to steam-launch 278 

torpedoes 275 

for boat service 275 

observations of floating obstruction committee 284 

sizes of boats most suitable for 289 

P. 

Passive obstructions, combination of, with submarine mines 24-271 

Paying out electric cables^ mode of 151 

Personal equation of observer 264 

Pickets, use of for cross-bearings at short distances 190 

Pile, voltaic, extemporized 183 

Platinum wire fuse 93-95 

battery for use with 172 

most approved form 304 

tests of 240 

Polarization, effect in disturbing tests 256 

Porter, Admiral, United States Navy, opinion of 11 

Position of mines, mode of marking J 51 

to be concealed 157 

Pressure, lateral, on buoyant mine, calculation for 86 

Primer, torpedo, Abel's, most approved form 88-304 

Principles, general, in defending a channel 22 

Projectile torpedoes ." 275 

use of 293 

Protection, outer, for electric cables c 127 

Q. 

Qualifications of cases for submarine mines 49 

of electric cables 115 

of officers and men for submarine mining duty 270 

Quantity batteries, tests of 253 

E. 

• 

Eeflecting electrometer 268 

galvanometer „ 268 

Eesistance coils 269 

electrical, of cable, test of 247 

Rheostat 269 

Eoatlstead, open, defense by submarine mines 26 

Rocket composition, torpedoes propelled by 293 

Eoom, testing, in a fort 159 

Eope protection for electric cables 127 

Rule, approximate, for determining size of charge 45 

Rules, general, in using submarine mines 20 

S. 

Sea-ceil, disturbing influence, during test 256 

test for insulation by *. 255 

torpedo, Harvey's 28 



316 

Page. 

Shutter signaling-apparatus for circuit-breaker 230 

combined with firing keys 234 

and firing apparatus 226 

most approved form 306 

Siemens Brothers', electric cables 116 

Signaling from fort to guard-boat and back 161 

Single line of mines, disadvantage of 22 

Sinker, mushroom, most approved form „ 303 

Slack to be allowed in paying out electric cables 152 

Special torpedo-vessels 275 

Speed to be slow when searching for submarine mines 274 

" Spnyten Duy vil," opinion of floating obstruction committee 277 

Steam-launch fitted with outrigger torpedo 278 

Submarine explosions, clearing channel by , 274 

mine, definition of 7 

mines, American 8 

Austrian 8 

Chinese 8 

defensive 10 

electrical 17 

advantages and disadvantages 17 

especially applicable to defense of the United Kingdom and 

colonies =. 14 

increase to defense by use of 15 

materials for, easily obtainable 15 

mechanical 16 

advantages 17 

danger in submersion 18 

disadvantages 16 

moral effect of , 14 

nature of 16 

Russian 8 

small, cost of 15 

Submersion, electrical tests during 156 

tests before and after 238-254 

T. 

Table, testing, Austrian ? , . . . 220 

simple „ 222 

and firing, Woolwich , 235 

Telegraph, electric, from fort to guard-boat - 161 

Telescope, fixed, and firing-key, use of 108 

Telescopic firing-keys 193 

most approved- form 305 

Tension-fuse, battery for use with 177 

tests of 242 

" Terpsichore," Her Majesty's ship, experiments on, to determine effect of a 

given charge 43 

Test for insulation by sea-cell 255 

discharge 246 

loop, Varley's 258 

of electrical resistance of cable. 247 

to ascertain whether charge is dry 254 

to discover position of fault in insulation 246 



317 

Tape. 

Testing-batteries 269 

and firing-table, "Woolwich 235 

box. for connection of multiple cable 124 

electrical instruments used in 268 

room in a fort 159 

table, Austrian 220 

simple 222 

Tests before and after submersion 238 

electrical 238 

during submergence 156 

of electric cables 245 

value due to comparison 258 

mechanical 238 

of electric cables 243 

of case 239 

of combined system before and after submersion 254 

of detonating fuses 243 

of explosives 239 

of frictioual electrical machine 250 

of instruments 239 

of mechanical fuses 240 

of mooring apparatus 240 

of multiple cables 246 

of platinum wire fuse 240 

of quantity batteries 253 

of tension fuse 242-265 

of voltaic batteries 250 

of water-tight and insulated joints 248 

of "Wheatstone's exploder 250 

Thermo-galvauometer 269 

Tide, mooring when rise and fall is considerable 82 

Torpedo, definition of 7 

drifting, Lewis' 294 

McEvoy's 294 

fish, Lupin and Whitehead's.. 291 

fired from boat 292 

outrigger, fitted to steam-launch 278 

primer, Abel's approved form 88-304 

sea, Harvey's 280 

Torpedoes, drifting 275-294 

nature of operations suitable for 295 

or offensive mines 9 

outrigger 275 

for boat service 275 

observations of floating obstruction committee 284 

sizes of boats most suitable for 289 

proj ectile 275 

use of 293 

propelled by rocket composition 293 

Tube, firing, Captain Harding Steward's 109 

V. 

Varley's loop-test 258 

Venice, project for defense by submarine mines 19 



318 

Page. 

Visual signaling from fort to guard-boat and back 161 

Voltaic battery, Austrian, for submarine mines 181 

Daniell's . . 179 

Muirhead's 180 

Varley 's 180 

for use with platinum fuse 172 

tension fuse 177 

Grove's 172 

ignition by 172 

Le Clanche' e 182-305 

Marie"-Davy , 179 

sand, Wollaston's 177 

Walker's 98-172 

batteries, tests of 250 

pile, extemporized 183 

Von Scheliha, observation on submarine mines , 19 

W. 

Walker's voltaic battery 98-172 

Wash of sea, protection of electric cables from 154 

Water-tight connection, temporary 134 

clay 135 

joints 130 

tests of 248 

Weather, favorable, necessary for mooring purposes 76 

Wire coils of instruments must be suited to currents to be conveyed 237 



NOTES 



TOKPEDOES, OFFENSIVE AND DEFENSIVE. 



MAJOR R, H. STOTHERD, R. E. 



WASHINGTON: 

GOVERNMENT FEINTING OFFICE 

18 7 2. 



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